1. Let list be a new array. @@ -2025,7 +2025,7 @@ The setProperty(property, va a {{NoModificationAllowedError}} exception and terminate these steps.
2. If property is not a custom property, follow these substeps:
   -
   1. Let property be property converted to ASCII lowercase. +
   2. Let property be property converted to ASCII lowercase.
   3. If property is not a case-sensitive match for a supported CSS property, terminate this algorithm.
3. If value is the empty string, invoke {{CSSStyleDeclaration/removeProperty()}} @@ -2067,7 +2067,7 @@ steps: a {{NoModificationAllowedError}} exception and terminate these steps.
4. If property is not a custom property, follow these substeps:
   -
   1. Let property be property converted to ASCII lowercase. +
   2. Let property be property converted to ASCII lowercase.
   3. If property is not a case-sensitive match for a supported CSS property, terminate this algorithm.
5. If value is the empty string, invoke {{CSSStyleDeclaration/removeProperty()}} @@ -2103,7 +2103,7 @@ these steps: a {{NoModificationAllowedError}} exception and terminate these steps.
6. If property is not a custom property, follow these substeps:
   -
   1. Let property be property converted to ASCII lowercase. +
   2. Let property be property converted to ASCII lowercase.
   3. If property is not a case-sensitive match for a supported CSS property, terminate this algorithm.
7. If priority is not the empty string and is not an ASCII case-insensitive match for the string @@ -2133,7 +2133,7 @@ The removeProperty(property)
8. If the readonly flag is set, throw a {{NoModificationAllowedError}} exception and terminate these steps.
9. If property is not a custom property, - let property be property converted to ASCII lowercase. + let property be property converted to ASCII lowercase.
10. Let value be the return value of invoking {{CSSStyleDeclaration/getPropertyValue()}} with property as argument.
11. If property is a shorthand property, for each longhand property longhand that property maps to, invoke @@ -2246,7 +2246,7 @@ The CSS property to IDL attribute algorithm for property,
12. If c is "-" (U+002D), let uppercase next be set.
13. Otherwise, if uppercase next is set, let uppercase next be unset and append c - converted to ASCII uppercase to output. + converted to ASCII uppercase to output.
14. Otherwise, append c to output.

1. If c is in the range U+0041 to U+005A (ASCII uppercase), append "-" (U+002D) followed by c - converted to ASCII lowercase to output. + converted to ASCII lowercase to output.
2. Otherwise, append c to output.

keyword

The keyword - converted to ASCII lowercase. + converted to ASCII lowercase.

<angle>

The <number> component serialized as per <number> followed by the unit in canonical form as defined in its respective specification. @@ -2489,7 +2489,7 @@ depends on the component, as follows: the literal string "s".

<uri> -

The absolute URL +

The absolute-URL string serialized as URL.

 SVGElement implements ElementCSSInlineStyle;

From de105a8b2cdea60ec2c51c1728ea074860a82080 Mon Sep 17 00:00:00 2001
From: Simon Sapin 
Date: Fri, 21 Apr 2017 12:19:25 +0900
Subject: [PATCH 2/5] [cssom] Use USVString for href attribute of Stylesheet
 and CSSImportRule

As resolved by CSS WG on 2017-04-19, because they are URLs.

This is consistent with HTML: https://github.com/whatwg/html/pull/1282
---
 cssom/Overview.bs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/cssom/Overview.bs b/cssom/Overview.bs
index c1a4e5a6179..aaf1ed61c21 100644
--- a/cssom/Overview.bs
+++ b/cssom/Overview.bs
@@ -809,7 +809,7 @@ The {{StyleSheet}} interface represents an abstract, base style sheet.
 
 interface StyleSheet {
   readonly attribute DOMString type;
-  readonly attribute DOMString? href;
+  readonly attribute USVString? href;
   readonly attribute (Element or ProcessingInstruction)? ownerNode;
   readonly attribute StyleSheet? parentStyleSheet;
   readonly attribute DOMString? title;
@@ -1650,7 +1650,7 @@ The CSSImportRule interface represents an @import at-r
 
 
 interface CSSImportRule : CSSRule {
-  readonly attribute DOMString href;
+  readonly attribute USVString href;
   [SameObject, PutForwards=mediaText] readonly attribute MediaList media;
   [SameObject] readonly attribute CSSStyleSheet styleSheet;
 };

From f23d1193d27dc700b0a66c0e12cf766cef62dbee Mon Sep 17 00:00:00 2001
From: Simon Sapin 
Date: Fri, 21 Apr 2017 12:28:09 +0900
Subject: [PATCH 3/5] [cssom] Add IDL `CSSOMString`, typedef of either
 USVString or DOMString

Implementations can choose one or the other.

CSSWG resolution:
https://github.com/w3c/csswg-drafts/issues/1217#issuecomment-295053842
---
 cssom/Overview.bs | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/cssom/Overview.bs b/cssom/Overview.bs
index aaf1ed61c21..9d91431c481 100644
--- a/cssom/Overview.bs
+++ b/cssom/Overview.bs
@@ -256,6 +256,41 @@ the last item. Unless otherwise specified, an empty list is serialized as the
 empty string.
 
 
+CSSOMString {#cssomstring-type}
+===============================
+
+Most strings in CSSOM interfaces use the CSSOMString type.
+Each implementation chooses to define it as either {{USVString}} or {{DOMString}}:
+
+
+typedef USVString CSSOMString;
+
+
+Or, alternatively:
+
+
+typedef DOMString CSSOMString;
+
+
+

+	The difference is only observable from web content
+	when surrogate code units are involved.
+	{{DOMString}} would preserve them,
+	whereas {{USVString}} would replace them with U+FFFD REPLACEMENT CHARACTER.
+
+	This choice effectively allows implementations to do this replacement,
+	but does not require it.
+
+	This enables an implementation to use UTF-8 internally to represent strings in memory.
+	Since well-formed UTF-8 specifically disallows surrogate code points,
+	it effectively requires this replacement.
+
+	On the other hand,
+	implementations that internally represent strings as 16-bit code units
+	may prefer to avoid the cost of doing this replacement.
+
+
+
 Media Queries {#media-queries}
 ==============================
 

From 9e5091066c201974df990562dc3f85394f0dfee0 Mon Sep 17 00:00:00 2001
From: Simon Sapin 
Date: Fri, 21 Apr 2017 14:39:57 +0900
Subject: [PATCH 4/5] [css-color] Remove unused DOMString term from "Ignored
 Terms".

---
 css-color/Overview.bs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/css-color/Overview.bs b/css-color/Overview.bs
index 61657e977a9..ef8f55a63cf 100644
--- a/css-color/Overview.bs
+++ b/css-color/Overview.bs
@@ -13,7 +13,7 @@ Former Editor: L. David Baron, Mozilla Corporation, dbaron@dbaron.org
 Abstract: This specification describes CSS <> values and properties for foreground color and group opacity.
 Repository: w3c/csswg-drafts
 Inline Github Issues: title
-Ignored Terms: stacking context, double, octet, DOMString
+Ignored Terms: stacking context, double, octet
 
 
 

From b937a928eef82003c0891654c578a8e035c00f91 Mon Sep 17 00:00:00 2001
From: Simon Sapin 
Date: Fri, 21 Apr 2017 14:42:38 +0900
Subject: [PATCH 5/5] [all] Replace most occurrences DOMString with
 CSSOMString.

CSSWG resolution:
https://github.com/w3c/csswg-drafts/issues/1217#issuecomment-295053842

Fix #1217.

Each occurrence is one of:

* CSS syntax
* A name (for example a property name) that also occurs in CSS syntax
* `Stylesheet::type`, which is always `text/css`.

Not replaced:

* `Stylesheet::title`, which is set from the eponymous HTML content attribute
  of [``](https://html.spec.whatwg.org/multipage/semantics.html#attr-style-title)
  and [``](https://html.spec.whatwg.org/multipage/semantics.html#attr-link-title)
  elements.
  These contant attributes are reflected as `HTMLElement::title` DOM attributes,
  where they are `DOMString`.
---
 css-animations-2/Overview.bs    | 16 ++++-----
 css-animations/Overview.bs      | 30 ++++++++---------
 css-conditional/Overview.bs     | 20 +++++------
 css-counter-styles/Overview.bs  | 48 +++++++++++++--------------
 css-font-loading/Overview.bs    | 42 +++++++++++------------
 css-fonts/Fonts.html            | 24 +++++++-------
 css-fonts/Fonts.src.html        | 24 +++++++-------
 css-fonts/Overview-wip.bs       | 22 ++++++------
 css-module-bikeshed/Overview.bs |  6 ++--
 css-pseudo/Overview.bs          |  6 ++--
 css-regions/Overview.bs         | 14 ++++----
 css-regions/region-styling.txt  |  2 +-
 css-transitions-2/Overview.bs   |  6 ++--
 css-transitions/Overview.bs     | 14 ++++----
 cssom-view/Overview.bs          | 10 +++---
 cssom/Overview.bs               | 59 +++++++++++++++++----------------
 mediaqueries/Overview.bs        |  8 ++---
 17 files changed, 176 insertions(+), 175 deletions(-)

diff --git a/css-animations-2/Overview.bs b/css-animations-2/Overview.bs
index 006f45bb38b..58aae8b8f32 100644
--- a/css-animations-2/Overview.bs
+++ b/css-animations-2/Overview.bs
@@ -540,7 +540,7 @@ the {{AnimationEvent}}.
 
 
 interface CSSAnimation : Animation {
-  readonly attribute DOMString animationName;
+  readonly attribute CSSOMString animationName;
 };
 
 
@@ -559,13 +559,13 @@ Perhaps something like the following:
 
 
 [Constructor (Animatable? target,
-              DOMString animationName,
+              CSSOMString animationName,
               optional (unrestricted double or KeyframeEffectOptions) options,
-              optional DOMString defaultEasing = "ease"),
+              optional CSSOMString defaultEasing = "ease"),
  Constructor (Animatable? target,
-              DOMString animationName,
+              CSSOMString animationName,
               (unrestricted double or KeyframeEffectOptions) options,
-              DOMString defaultEasing,
+              CSSOMString defaultEasing,
               AnimationTimeline? timeline)]
 partial interface CSSAnimation { };
 
@@ -580,10 +580,10 @@ updating the set of keyframes returned by
 Something like,
 
 
-[Constructor (DOMString keyframesName, DOMString defaultEasing)]
+[Constructor (CSSOMString keyframesName, CSSOMString defaultEasing)]
 interface CSSKeyframeEffectReadOnly : KeyframeEffectReadOnly {
-  readonly attribute DOMString keyframesName;
-  readonly attribute DOMString defaultEasing;
+  readonly attribute CSSOMString keyframesName;
+  readonly attribute CSSOMString defaultEasing;
 };
 
 
diff --git a/css-animations/Overview.bs b/css-animations/Overview.bs
index 13a68bb7ad3..154e5936f96 100644
--- a/css-animations/Overview.bs
+++ b/css-animations/Overview.bs
@@ -909,16 +909,16 @@ The AnimationEvent Interface
 IDL Definition
 
 	
-		[Constructor(DOMString type, optional AnimationEventInit animationEventInitDict)]
+		[Constructor(CSSOMString type, optional AnimationEventInit animationEventInitDict)]
 		interface AnimationEvent : Event {
-		  readonly attribute DOMString animationName;
+		  readonly attribute CSSOMString animationName;
 		  readonly attribute float elapsedTime;
-		  readonly attribute DOMString pseudoElement;
+		  readonly attribute CSSOMString pseudoElement;
 		};
 		dictionary AnimationEventInit : EventInit {
-		  DOMString animationName = "";
+		  CSSOMString animationName = "";
 		  float elapsedTime = 0.0;
-		  DOMString pseudoElement = "";
+		  CSSOMString pseudoElement = "";
 		};
 	
 
@@ -926,7 +926,7 @@ IDL Definition
 Attributes
 
 	

-		
animationName, of type DOMString, readonly
+		
animationName, of type CSSOMString, readonly
 		

 			The value of the 'animation-name' property of the animation that fired the event.
 		
elapsedTime, of type float, readonly
@@ -934,7 +934,7 @@ Attributes
 			The amount of time the animation has been running, in seconds, when this event fired,
 			excluding any time the animation was paused. The precise calculation for
 			of this member is defined along with each event type.
-		
pseudoElement, of type DOMString, readonly
+		
pseudoElement, of type CSSOMString, readonly
 		

 			The name (beginning with two colons) of the CSS pseudo-element on which the animation
 			runs (in which case the target of the event is that pseudo-element's corresponding
@@ -1091,7 +1091,7 @@ IDL Definition
 
 	
 	interface CSSKeyframeRule : CSSRule {
-    attribute DOMString keyText;
+    attribute CSSOMString keyText;
     [SameObject, PutForwards=cssText] readonly attribute CSSStyleDeclaration style;
 	};
 	
@@ -1143,12 +1143,12 @@ IDL Definition
 
 	
 	interface CSSKeyframesRule : CSSRule {
-	           attribute DOMString   name;
+	           attribute CSSOMString   name;
 	  readonly attribute CSSRuleList cssRules;
 
-	  void            appendRule(DOMString rule);
-	  void            deleteRule(DOMString select);
-	  CSSKeyframeRule? findRule(DOMString select);
+	  void            appendRule(CSSOMString rule);
+	  void            deleteRule(CSSOMString select);
+	  CSSKeyframeRule? findRule(CSSOMString select);
 	};
 	
 
@@ -1181,7 +1181,7 @@ The appendRule method
 
 	

 
-		
rule of type DOMString
+		
rule of type CSSOMString
 		

 			The rule to be appended, expressed in the same syntax as one entry in the
 			''@keyframes'' rule. A valid rule is always appended e.g. even if its key(s) already
@@ -1203,7 +1203,7 @@ The deleteRule method
 
 	

 
-		
select of type DOMString
+		
select of type CSSOMString
 		

 			The keyframe selector of the rule to be deleted: a comma-separated list of percentage values between 0% and 100% or the keywords ''from'' or ''to'' which resolve to 0% and 100%, respectively.
 
@@ -1225,7 +1225,7 @@ The findRule method
 	Parameters:
 
 	

-		
select of type DOMString
+		
select of type CSSOMString
 		

 			The keyframe selector of the rule to be deleted: a comma-separated list of percentage values between 0% and 100% or the keywords ''from'' or ''to'' which resolve to 0% and 100%, respectively.
 
diff --git a/css-conditional/Overview.bs b/css-conditional/Overview.bs
index 4913fcf1029..3d6b300e77d 100644
--- a/css-conditional/Overview.bs
+++ b/css-conditional/Overview.bs
@@ -834,7 +834,7 @@ The CSSGroupingRule interface
 
 interface CSSGroupingRule : CSSRule {
     readonly attribute CSSRuleList cssRules;
-    unsigned long insertRule (DOMString rule, unsigned long index);
+    unsigned long insertRule (CSSOMString rule, unsigned long index);
     void deleteRule (unsigned long index);
 };
 
@@ -846,7 +846,7 @@ interface CSSGroupingRule : CSSRule {
 
 
 

-  
insertRule(DOMString rule, unsigned long index), returns
+  
insertRule(CSSOMString rule, unsigned long index), returns
     unsigned long
   

     The insertRule operation must
@@ -890,13 +890,13 @@ all the “conditional” at-rules,
 
 
 interface CSSConditionRule : CSSGroupingRule {
-    attribute DOMString conditionText;
+    attribute CSSOMString conditionText;
 };
 
 
 

 
-  
conditionText of type DOMString
+  
conditionText of type CSSOMString
   

     
The conditionText attribute represents
     the condition of the rule.
@@ -940,7 +940,7 @@ interface CSSMediaRule : CSSConditionRule {
   
The media attribute must return a MediaList object
     for the list of media queries specified with the ''@media'' rule.
 
-  
conditionText of type DOMString (CSSMediaRule-specific definition for attribute on CSSConditionRule)
+  
conditionText of type CSSOMString (CSSMediaRule-specific definition for attribute on CSSConditionRule)
   
The conditionText attribute (defined on the CSSConditionRule parent rule),
     on getting, must return the value of media.mediaText on the rule.
 
@@ -960,7 +960,7 @@ interface CSSSupportsRule : CSSConditionRule {
 
 
 

-  
conditionText of type DOMString (CSSSupportsRule-specific definition for attribute on CSSConditionRule)
+  
conditionText of type CSSOMString (CSSSupportsRule-specific definition for attribute on CSSConditionRule)
   
The conditionText attribute (defined on the CSSConditionRule parent rule),
     on getting, must return the condition that was specified,
     without any logical simplifications,
@@ -998,15 +998,15 @@ The {{CSS}} interface holds useful CSS-related functions that do not belong else
 
 
 partial interface CSS {
-  static boolean supports(DOMString property, DOMString value);
-  static boolean supports(DOMString conditionText);
+  static boolean supports(CSSOMString property, CSSOMString value);
+  static boolean supports(CSSOMString conditionText);
 };
 
 
 

-  
supports(DOMString property, DOMString value),
+  
supports(CSSOMString property, CSSOMString value),
     returns boolean
-  
supports(DOMString conditionText),
+  
supports(CSSOMString conditionText),
     returns boolean
   

     When the supports() method is invoked with two arguments property and value,
diff --git a/css-counter-styles/Overview.bs b/css-counter-styles/Overview.bs
index fbe5090db25..5eacbd5ab38 100644
--- a/css-counter-styles/Overview.bs
+++ b/css-counter-styles/Overview.bs
@@ -2480,24 +2480,24 @@ The CSSCounterStyleRule interface
 
 	
 	interface CSSCounterStyleRule : CSSRule {
-	  attribute DOMString name;
-	  attribute DOMString system;
-	  attribute DOMString symbols;
-	  attribute DOMString additiveSymbols;
-	  attribute DOMString negative;
-	  attribute DOMString prefix;
-	  attribute DOMString suffix;
-	  attribute DOMString range;
-	  attribute DOMString pad;
-	  attribute DOMString speakAs;
-	  attribute DOMString fallback;
+	  attribute CSSOMString name;
+	  attribute CSSOMString system;
+	  attribute CSSOMString symbols;
+	  attribute CSSOMString additiveSymbols;
+	  attribute CSSOMString negative;
+	  attribute CSSOMString prefix;
+	  attribute CSSOMString suffix;
+	  attribute CSSOMString range;
+	  attribute CSSOMString pad;
+	  attribute CSSOMString speakAs;
+	  attribute CSSOMString fallback;
 	};
 	
 
 	

-		
name of type DOMString
+		
name of type CSSOMString
 		

-			The name attribute on getting must return a DOMString object
+			The name attribute on getting must return a CSSOMString object
 			that contains the serialization of the <> defined for the associated rule.
 
 			On setting the name attribute, run the following steps:
@@ -2517,18 +2517,18 @@ The CSSCounterStyleRule interface
 				
Otherwise, do nothing.