RenderTextHarfBuzz: treat 「」 as brackets.

Brackets have the "common script" unicode property and need special handling
when breaking runs (see http://www.unicode.org/reports/tr24/#Common ).

Currently, emoji breaks runs correctly around other bracket and quote mark
types, but not around 「」, which is commonly used in CJK languages.

Bug: 843426, 396776
Change-Id: Ia5ff5165d5c260aa1876488e2f51d566f2164cd6
Reviewed-on: https://chromium-review.googlesource.com/1146401Reviewed-by: Michael Wasserman <msw@chromium.org>
Commit-Queue: Trent Apted <tapted@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577345}

ui/gfx/render_text_harfbuzz.cc

@@ -65,10 +65,13 @@ bool IsUnusualBlockCode(UBlockCode block_code) {
          block_code == UBLOCK_MISCELLANEOUS_SYMBOLS;
 }
 
+// Returns true if |character| is a bracket. This is used to avoid "matching"
+// brackets picking different font fallbacks, thereby appearing mismatched.
 bool IsBracket(UChar32 character) {
-  static const char kBrackets[] = { '(', ')', '{', '}', '<', '>', };
-  static const char* kBracketsEnd = kBrackets + arraysize(kBrackets);
-  return std::find(kBrackets, kBracketsEnd, character) != kBracketsEnd;
+  // 0x300c and 0x300d are「foo」 style brackets.
+  constexpr UChar32 kBrackets[] = {'(', ')', '{',       '}',
+                                   '<', '>', L'\u300c', L'\u300d'};
+  return base::ContainsValue(kBrackets, character);
 }
 
 // If the given scripts match, returns the one that isn't USCRIPT_INHERITED,

ui/gfx/render_text_unittest.cc

@@ -4004,6 +4004,13 @@ TEST_P(RenderTextHarfBuzzTest, HarfBuzz_BreakRunsByEmoji) {
   EXPECT_EQ(ToString16Vec({"x", "😁", "y", "✨"}), GetRunListStrings());
   // U+1F601 is represented as a surrogate pair in UTF-16.
   EXPECT_EQ("[0][1->2][3][4]", GetRunListStructureString());
+
+  // Ensure non-latin 「foo」 brackets around Emoji correctly break runs.
+  render_text->SetText(UTF8ToUTF16("「🦋」「"));
+  test_api()->EnsureLayout();
+  EXPECT_EQ(ToString16Vec({"「", "🦋", "」「"}), GetRunListStrings());
+  // Note 🦋 is a surrogate pair [1->2].
+  EXPECT_EQ("[0][1->2][3->4]", GetRunListStructureString());
 }
 
 TEST_P(RenderTextHarfBuzzTest, HarfBuzz_BreakRunsByEmojiVariationSelectors) {