Fix generic font family issue on Android

Source/core/css/CSSFontSelector.cpp

Index: Source/core/css/CSSFontSelector.cpp
diff --git a/Source/core/css/CSSFontSelector.cpp b/Source/core/css/CSSFontSelector.cpp
index a15bf91dd170b804f130c4a6300cbe7fe83a3c8b..618fea40bc886a21d0a330f333604346dc8f4d91 100644
--- a/Source/core/css/CSSFontSelector.cpp
+++ b/Source/core/css/CSSFontSelector.cpp
@@ -156,12 +156,15 @@ static AtomicString familyNameFromSettings(const GenericFontFamilySettings& sett
 {
     UScriptCode script = fontDescription.script();
 
+#if OS(ANDROID)
     if (fontDescription.genericFamily() == FontDescription::StandardFamily && !fontDescription.isSpecifiedFont())
-        return settings.standard(script);
+        return FontCache::getGenericFamilyNameForScript(FontFamilyNames::webkit_standard, script);

[dglazkov, 2014/02/28 21:30:30]

This is okay, but can we not instead unfork this codepath? Effectively,
getGenericFamilyNameForScript does the same thing as
FontCache::getFontFamilyForCharacter, and we shouldn't need to call it here?

[Xianzhu, 2014/02/28 22:15:12]

FontCache::getFontFamilyForCharacter doesn't actually work for multiple locales,
because we don't have separated entries for different locales in a single glyph
tree. To make it work we need an additional field m_locale in FontDescription
and FontData, so that we can distinguish different locales of them. I tried this
method several months ago in https://codereview.chromium.org/23503080/, but
finally chose https://codereview.chromium.org/24622002/ because of the
complexity and uncertainty about memory and performance of the former.

Actually we have already distinguished locales at the top level if different
locales has different font families for generic font families. This seems more
efficient than distinguish locales at each GlyphPageTreeNode. For now we require
glyphs in one glyph tree are for the same locale. Breaking this causes bugs,
like this one, and crbug.com/348078.

The forked codepath for Android is to meet the above requirement.

I think crbug.com/348078 can also be resolved with the similar method.

 
-#if OS(ANDROID)
-    return FontCache::getGenericFamilyNameForScript(genericFamilyName, script);
+    if (genericFamilyName.startsWith("-webkit-"))
+        return FontCache::getGenericFamilyNameForScript(genericFamilyName, script);
 #else
+    if (fontDescription.genericFamily() == FontDescription::StandardFamily && !fontDescription.isSpecifiedFont())
+        return settings.standard(script);
     if (genericFamilyName == FontFamilyNames::webkit_serif)
         return settings.serif(script);
     if (genericFamilyName == FontFamilyNames::webkit_sans_serif)