[css-inline-3] Improve line height intro and titling

Author: fantasai

css-inline-3/Overview.bs

@@ -919,7 +919,12 @@ Legacy Values for SVG</h5>
 	Issue: We would prefer to remove the ''baseline-shift/baseline'' value, and are looking for feedback from SVG user agents as to whether it's necessary.
 
 <h2 id="line-height">
-Line Sizing and Spacing</h2>
+Logical Heights and Inter-line Spacing</h2>
+
+	The [=block-axis=] sizing of a [=line box=]
+	depends on the sizes and [[#alignment|alignment]] of its [=inline-level=] contents.
+	This sizing is controlled by
+	the 'line-height', 'text-edge', 'leading-trim', and 'inline-sizing' properties.
 
 <h3 id="line-height-property">
 Line Spacing: the 'line-height' property</h3>
@@ -1118,7 +1123,7 @@ Inline Box Edge Metrics: the 'text-edge' property</h3>
 
 
 <h3 id="inline-height">
-Logical Height Contributions of Inline Boxes</h3>
+Calculating the Logical Height Contributions (“Layout Bounds”) of Inline Boxes</h3>
 
 	The contribution of an [=inline box=] to the [=logical height=] of its [=line box=],
 	here referred to as its <dfn>layout bounds</dfn>,
@@ -1371,11 +1376,8 @@ Half-Leading Control: the 'leading-trim' property</h3>
 	Note: The [=block-end=] side does not coincide with the [=line-under=] side
 	when 'writing-mode' is ''vertical-lr''.
 
-<h2 id="inline-box-dimensions">
-Drawing Inline Boxes</h2>
-
 <h3 id="line-fill">
-Inline Box Heights: the 'inline-sizing' property</h3>
+Inline Box Drawing Height: the 'inline-sizing' property</h3>
 
 	<pre class="propdef">
 	Name: inline-sizing