text-emphasis: Do not paint emphasis marks on punctuations

* Do not paint emphasis marks on punctuations
* Do not use IDEOGRAPHIC FULL STOP for text-combine placeholder
  It's a punctuation.  Use HIRAGANA LETTER A instead.
* Do not paint emphasis marks on generated ellipsis symbols just in case
  It's always a punctuation now. But we might support arbitrary string
  in the future.

* Update text-emphasis-punctuation-1.html so that it uses Ahem font
  Without this change, the test had pixel glitches on Chromium.

The new behavior matches to Firefox.

https://drafts.csswg.org/css-text-decor/#text-emphasis-style-property

Bug: 359420112
Change-Id: If93ef6190e739a0cf64d3becb24c41191dbe1100
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6108987
Commit-Queue: Koji Ishii <[email protected]>
Auto-Submit: Kent Tamura <[email protected]>
Reviewed-by: Koji Ishii <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1400253}

css/css-text-decor/text-emphasis-punctuation-1-ref.html

@@ -2,11 +2,13 @@
 <meta charset="utf-8">
 <title>CSS text decoration test: emphasis marks and punctuation</title>
 
+<link rel="stylesheet" type="text/css" href="/fonts/ahem.css">
 <style>
+.ahem { font-family: Ahem; }
 span { text-emphasis: filled circle; }
 </style>
 
 <p>The punctuation should <b>not</b> have emphasis marks:</p>
-<p><span>Abc</span> (<span>def</span>) <span>gh</span>? <span>Ijk</span>.
+<p class="ahem"><span>Abc</span> (<span>def</span>) <span>gh</span>? <span>Ijk</span>.
 <span>Lm</span>, <span>n</span>-<span>op</span>!
 [<span>Qrst</span>…<span>uv</span>] <span>wx</span>/<span>yz</span>.</p>

css/css-text-decor/text-emphasis-punctuation-1.html

@@ -5,8 +5,9 @@
 <link rel="help" href="https://drafts.csswg.org/css-text-decor/#text-emphasis-style-property">
 <meta name="assert" content="emphasis marks are not drawn for punctuation (with a small set of exceptions)">
 
+<link rel="stylesheet" type="text/css" href="/fonts/ahem.css">
 <style>
-.emph { text-emphasis: filled circle; }
+.emph { text-emphasis: filled circle; font-family: Ahem; }
 </style>
 
 <p>The punctuation should <b>not</b> have emphasis marks:</p>