Handle U+3099/309A Kana Voiced Sound Marks in complex path

Source/platform/fonts/UTF16TextIterator.h

Index: Source/platform/fonts/UTF16TextIterator.h
diff --git a/Source/platform/fonts/UTF16TextIterator.h b/Source/platform/fonts/UTF16TextIterator.h
index c988cd9f900c5241c3fed25d3633e9955b0923da..4aabdbbb85690cd4057e4f9683b35fff9917c906 100644
--- a/Source/platform/fonts/UTF16TextIterator.h
+++ b/Source/platform/fonts/UTF16TextIterator.h
@@ -45,7 +45,11 @@ public:
         character = *m_characters;
         m_currentGlyphLength = 1;
 
-        if (character < hiraganaLetterSmallACharacter || consumeSlowCase(character)) {
+        if (!U16_IS_SURROGATE(character) || consumeSurrogatePair(character)) {
+            // TODO(kojii): This looks broken, we should actually check whether

[drott, 2015/07/17 15:15:58]

Minor: I'd suggest to move this comment to a bug report, e.g. "Check
UTF16TextITerator's category mask behavior" and explain the overlap with
HarfBuzz there. In my opinion, here in the code it does not add much without
knowing the context.

[kojii, 2015/07/17 16:32:58]

Moved to crbug.com/511306, thanks for the advice!

+            // the *next* character is U_GC_M_MASK or not.
+            // Also this is redundant with what HarfBuzzShaper does. Either one
+            // should be removed once the simple path is gone: crbug.com/404597
             if (U_GET_GC_MASK(character) & U_GC_M_MASK)
                 consumeMultipleUChar();
             return true;
@@ -68,9 +72,8 @@ public:
     unsigned glyphLength() const { return m_currentGlyphLength; }
 
 private:
-    bool consumeSlowCase(UChar32&);
+    bool consumeSurrogatePair(UChar32&);
     void consumeMultipleUChar();
-    UChar32 normalizeVoicingMarks();
 
     const UChar* m_characters;
     const UChar* m_charactersEnd;