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

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

Index: third_party/WebKit/Source/platform/fonts/win/FontCacheSkiaWin.cpp
diff --git a/third_party/WebKit/Source/platform/fonts/win/FontCacheSkiaWin.cpp b/third_party/WebKit/Source/platform/fonts/win/FontCacheSkiaWin.cpp
index 9e2f7619b4f1354be3089543ae8859c1a46f10c1..841f46ac90520526b94c3db92c108da9a27ab1c3 100644
--- a/third_party/WebKit/Source/platform/fonts/win/FontCacheSkiaWin.cpp
+++ b/third_party/WebKit/Source/platform/fonts/win/FontCacheSkiaWin.cpp
@@ -52,6 +52,8 @@ int32_t FontCache::s_smallCaptionFontHeight = 0;
 AtomicString* FontCache::s_statusFontFamilyName = 0;
 int32_t FontCache::s_statusFontHeight = 0;
 
+UScriptCode FontCache::m_preferredScriptForHan = USCRIPT_COMMON;
+
 namespace {
 
 int32_t ensureMinimumFontHeightIfNeeded(int32_t fontHeight)
@@ -112,9 +114,25 @@ FontCache::FontCache()
     m_fontManager = adoptPtr(fontManager);
 }
 
-void FontCache::acceptLanguagesChanged(const String&)
+void FontCache::acceptLanguagesChanged(const String& acceptLanguages)
 {
-    // TODO(kojii): Take acceptLanguages into account for ambiguos scripts.
+    // Use the UI locale if it can disambiguate the Unified Han.
+    // Since Chrome synchronizes the ICU default locale with its UI locale,
+    // this ICU locale tells the current UI locale of Chrome.
+    m_preferredScriptForHan = scriptCodeForHanFromLocale(
+        icu::Locale::getDefault().getName(), '_');
+    if (m_preferredScriptForHan != USCRIPT_COMMON)
+        return;
+
+    // Use acceptLanguages if it has languages that can disambiguate.
+    Vector<String> languages;
+    acceptLanguages.split(',', languages);
+    for (String token : languages) {
+        token = token.stripWhiteSpace();
+        m_preferredScriptForHan = scriptCodeForHanFromLocale(token);
+        if (m_preferredScriptForHan != USCRIPT_COMMON)
+            return;
+    }
 }
 
 // Given the desired base font, this will create a SimpleFontData for a specific