Implement the ic-height metric of font-size-adjust

This change introduces support for the ic-height metric in
font-size-adjust [1], allowing developers to adjust font size based on
the height of the CJK water glyph. Notably, in cases where the chosen
font lacks the CJK water glyph or vertical font information, there is no
specified fallback behavior in the current specification. We adopt the
approach of combining ascent and descent for fallback, similar to
Gecko's method [2], until a standard fallback behavior is defined [3].

[1] https://www.w3.org/TR/css-fonts-5/#valdef-font-size-adjust-ic-height
[2] w3c/csswg-drafts#8792 (comment)
[3] w3c/csswg-drafts#6384

Test:
animations/responsive/interpolation/font-size-adjust-responsive.html
external/wpt/css/css-fonts/animations/font-size-adjust-composition.html
external/wpt/css/css-fonts/font-size-adjust-ic-height.html (new)
external/wpt/css/css-fonts/parsing/font-size-adjust-computed.html
external/wpt/css/css-fonts/parsing/font-size-adjust-valid.html

Bug: 1219875
Change-Id: Ie90a6241cb7e8a55fcaf65df5a4edc1058028ebe

Author: shivamidow

css/css-fonts/font-size-adjust-ic-height-ref.html

@@ -0,0 +1,27 @@
+>
+<meta charset="UTF-8">
+<title>font-size-adjust with the ic-height metrictitle>
+<link rel="author" title="ChangSeok Oh" href="mailto:[email protected]" />
+<link rel="stylesheet" type="text/css" href="/fonts/ahem.css" />
+<style>
+@font-face {
+  font-family: NotoSansCJK;
+  src: url(/fonts/noto/cjk/NotoSansCJKjp-Regular-subset-chws.otf);
+}
+div {
+  color: green;
+  background: green;
+  writing-mode: vertical-rl;
+  text-orientation: upright;
+}
+.adjustedRef {
+  font-family: NotoSansCJK;
+  font-size: 200px;
+}
+.notAdjustedRef {
+  font-family: Ahem;
+  font-size: 100px;
+}
+style>
+<div class="adjustedRef">水div>
+<div class="notAdjustedRef">水div>

css/css-fonts/font-size-adjust-ic-height.tentative.html

@@ -0,0 +1,36 @@
+>
+
+<meta charset="UTF-8">
+<title>font-size-adjust with the ic-height metrictitle>
+<link rel="author" title="ChangSeok Oh" href="mailto:[email protected]" />
+<link rel="help" href="https://www.w3.org/TR/css-fonts-5/#valdef-font-size-adjust-ic-height" />
+<link rel="match" href="font-size-adjust-ic-height-ref.html" />
+<link rel="stylesheet" type="text/css" href="/fonts/ahem.css" />
+<meta name="assert" content="Test checks whether font-size-adjust with the ic-height metric adjusts font size.">
+<style>
+@font-face {
+  font-family: NotoSansCJK;
+  src: url(/fonts/noto/cjk/NotoSansCJKjp-Regular-subset-chws.otf);
+}
+div {
+  font-size: 100px;
+  background: green;
+  color: green;
+  writing-mode: vertical-rl;
+  text-orientation: upright;
+}
+.adjusted {
+  font-family: NotoSansCJK;
+  /* The NotoSansCJK font has 1.0 as an aspect value for the CJK water glyph
+     (i.e., the advance height of “水” / the font size).
+     Therefore, an ic-height 2.0 means a 200% scaling up. */
+  font-size-adjust: ic-height 2.0;
+}
+.notAdjusted {
+  font-family: Ahem;
+  /* The Ahem font lacks vertical metrics, so no adjustment is applied. */
+  font-size-adjust: ic-height 0.5;
+}
+style>
+<div class="adjusted">水div>
+<div class="notAdjusted">水div>