Apply a fallback for font-size-adjust: ic-height when a required font metric is missing.

The W3C CSS WG resolved font-size-adjust with missing metrics by
applying the same way we do for other missing typographical units [1].
This CL aims to align with the resolution.

[1] w3c/csswg-drafts#6384 (comment)

Bug: 346773386, 325981757
Change-Id: I9dadf89c7e95b249ae149df7d15ccc0f55ea760a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5637274
Reviewed-by: Dominik Röttsches <[email protected]>
Commit-Queue: ChangSeok Oh <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1317246}

Author: shivamidow

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

@@ -18,10 +18,10 @@
   font-family: NotoSansCJK;
   font-size: 200px;
 }
-.notAdjustedRef {
+.fallbackRef {
   font-family: Ahem;
-  font-size: 100px;
+  font-size: 50px;
 }
 </style>
 <div class="adjustedRef">水</div>
-<div class="notAdjustedRef">水</div>
+<div class="fallbackRef">水</div>

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

@@ -26,11 +26,11 @@
      Therefore, an ic-height 2.0 means a 200% scaling up. */
   font-size-adjust: ic-height 2.0;
 }
-.notAdjusted {
+.fallback {
   font-family: Ahem;
-  /* The Ahem font lacks vertical metrics, so no adjustment is applied. */
+  /* The Ahem font lacks vertical metrics, so a fallback is applied. */
   font-size-adjust: ic-height 0.5;
 }
 </style>
 <div class="adjusted">水</div>
-<div class="notAdjusted">水</div>
+<div class="fallback">水</div>