[mediaqueries] Replace "screen" with "Web-exposed screen area" where relevant

This protects privacy by limited the amount information UAs are required
to expose.

This commit also reduces usage of the ambiguous word "screen" where it was
inaccurate or unneeded.

Closes w3c#426

Author: frivoal

mediaqueries/Overview.bs

@@ -946,10 +946,10 @@ Error Handling</h3>
 -->
 
 <h2 id="mf-dimensions">
-Screen/Device Dimensions Media Features</h2>
+Viewport/Page Dimensions Media Features</h2>
 
 <h3 id="width">
-Screen Width: the 'width' feature</h3>
+Width: the 'width' feature</h3>
 
 	<pre class='descdef mq'>
 	Name: width
@@ -993,7 +993,7 @@ Screen Width: the 'width' feature</h3>
 
 
 <h3 id="height">
-Screen Height: the 'height' feature</h3>
+Height: the 'height' feature</h3>
 
 	<pre class='descdef mq'>
 	Name: height
@@ -1011,7 +1011,7 @@ Screen Height: the 'height' feature</h3>
 	Negative <<length>>s are invalid.
 
 <h3 id='aspect-ratio'>
-Screen Aspect-Ratio: the 'aspect-ratio' feature</h3>
+Aspect-Ratio: the 'aspect-ratio' feature</h3>
 
 	<pre class='descdef mq'>
 	Name: aspect-ratio
@@ -1031,7 +1031,7 @@ Screen Aspect-Ratio: the 'aspect-ratio' feature</h3>
 
 
 <h3 id='orientation'>
-Screen Orientation: the 'orientation' feature</h3>
+Orientation: the 'orientation' feature</h3>
 
 	<pre class='descdef mq'>
 	Name: orientation
@@ -1070,7 +1070,7 @@ Screen Orientation: the 'orientation' feature</h3>
 Display Quality Media Features</h2>
 
 <h3 id="resolution">
-Screen Resolution: the 'resolution' feature</h3>
+Display Resolution: the 'resolution' feature</h3>
 
 	<pre class='descdef mq'>
 	Name: resolution
@@ -1133,7 +1133,7 @@ Screen Resolution: the 'resolution' feature</h3>
 
 
 <h3 id="scan">
-Screen Display Type: the 'scan' feature</h3>
+Display Type: the 'scan' feature</h3>
 
 	<pre class='descdef mq'>
 	Name: scan
@@ -1209,7 +1209,7 @@ Detecting Console Displays: the 'grid' feature</h3>
 
 
 <h3 id="update">
-Screen Update Frequency: the 'update' feature</h3>
+Display Update Frequency: the 'update' feature</h3>
 
 	<pre class='descdef mq'>
 	Name: update
@@ -1341,7 +1341,7 @@ Color Media Features</h2>
 
 
 <h3 id="color">
-Screen Color Depth: the 'color' feature</h3>
+Color Depth: the 'color' feature</h3>
 
 	<pre class='descdef mq'>
 	Name: color
@@ -2018,7 +2018,7 @@ device-width</h3>
 	</pre>
 
 	The 'device-width' media feature describes the width of the rendering surface of the output device.
-	For continuous media, this is the width of the screen.
+	For continuous media, this is the width of the <a>Web-exposed screen area</a>.
 	For paged media, this is the width of the page sheet size.
 
 	Negative <<length>>s are invalid.
@@ -2047,7 +2047,7 @@ device-height</h3>
 	</pre>
 
 	The 'device-height' media feature describes the height of the rendering surface of the output device.
-	For continuous media, this is the height of the screen.
+	For continuous media, this is the height of the <a>Web-exposed screen area</a>.
 	For paged media, this is the height of the page sheet size.
 
 	Negative <<length>>s are invalid.
@@ -2124,7 +2124,8 @@ The following changes were made to this specification since the
 		All media types except for ''screen'', ''print'', ''speech'', and ''all'' are deprecated.
 
 	<li>
-		Deprecated 'device-width', 'device-height', 'device-aspect-ratio'
+		Deprecated 'device-width', 'device-height', 'device-aspect-ratio',
+		and made them refer to the <a>Web-exposed screen area</a> instead of the screen for privacy and security reasons.
 </ul>
 
 
@@ -2172,3 +2173,10 @@ making this a somewhat more robust detection technique.
 
 That said, the information granted by Media Queries is relatively coarse,
 and does not contribute much entropy in this regard.
+
+A few legacy Media Features ('device-width', 'device-height', and 'device-aspect-ratio')
+expose information about the environment in which the UA is running
+without any clear benefit to doing so.
+They are retained for compatibility reasons,
+but for the sake of privacy and security,
+UAs have been allowed to report inacurate information.