Take Accept-Language into account in CJK font fallback for Windows

third_party/WebKit/Source/platform/fonts/win/FontFallbackWin.cpp

Index: third_party/WebKit/Source/platform/fonts/win/FontFallbackWin.cpp
diff --git a/third_party/WebKit/Source/platform/fonts/win/FontFallbackWin.cpp b/third_party/WebKit/Source/platform/fonts/win/FontFallbackWin.cpp
index 0ff4e29e69e5cd8f1d5be0ec3091d2ed64fe8c2e..a64f1c4c8a5a8294c4518ae2f8f04cd6ac40918a 100644
--- a/third_party/WebKit/Source/platform/fonts/win/FontFallbackWin.cpp
+++ b/third_party/WebKit/Source/platform/fonts/win/FontFallbackWin.cpp
@@ -230,6 +230,18 @@ void initializeScriptFontMap(ScriptToFontMap& scriptFontMap, SkFontMgr* fontMana
         scriptFontMap[USCRIPT_HAN] = localeFamily;
 }
 
+static UScriptCode scriptForHan(UScriptCode contentScript,
+    const AtomicString& contentLocale)
+{
+    UScriptCode script = scriptCodeForHanFromLocale(contentScript, contentLocale);
+    if (script != USCRIPT_COMMON)
+        return script;
+    script = FontCache::preferredScriptForHan();
+    if (script != USCRIPT_COMMON)
+        return script;
+    return USCRIPT_HAN;
+}
+
 // There are a lot of characters in USCRIPT_COMMON that can be covered
 // by fonts for scripts closely related to them. See
 // http://unicode.org/cldr/utility/list-unicodeset.jsp?a=[:Script=Common:]
@@ -408,13 +420,10 @@ const UChar* getFallbackFamily(UChar32 character,
     if (script == USCRIPT_COMMON)
         script = getScriptBasedOnUnicodeBlock(character);
 
-    // For unified-Han scripts, try the lang attribute.
-    if (script == USCRIPT_HAN) {
-        script = scriptCodeForHanFromLocale(contentScript, contentLocale);
-        // Use the UI locale if it is still ambiguous.
-        if (script == USCRIPT_COMMON)
-            script = USCRIPT_SIMPLIFIED_HAN;
-    }
+    // For unified-Han scripts, try the lang attribute, system, or
+    // accept-languages.
+    if (script == USCRIPT_HAN)
+        script = scriptForHan(contentScript, contentLocale);
 
     family = getFontFamilyForScript(script, generic, fontManager);
     // Another lame work-around to cover non-BMP characters.