Extend FontCache fallback API to support FontFallbackPriority

third_party/WebKit/Source/platform/fonts/linux/FontCacheLinux.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *     notice, this list of conditions and the following disclaimer in the
@@ skipping 32 matching lines @@
         WebFontInfo::fallbackFontForChar(c, preferredLocale, &webFallbackFont);
     fallbackFont->name = String::fromUTF8(CString(webFallbackFont.name));
     fallbackFont->filename = webFallbackFont.filename;
     fallbackFont->fontconfigInterfaceId = webFallbackFont.fontconfigInterfaceId;
     fallbackFont->ttcIndex = webFallbackFont.ttcIndex;
     fallbackFont->isBold = webFallbackFont.isBold;
     fallbackFont->isItalic = webFallbackFont.isItalic;
 }
 
 #if !OS(ANDROID)
-PassRefPtr<SimpleFontData> FontCache::fallbackFontForCharacter(const FontDescription& fontDescription, UChar32 c, const SimpleFontData*)
+PassRefPtr<SimpleFontData> FontCache::fallbackFontForCharacter(
+    const FontDescription& fontDescription,
+    UChar32 c,
+    const SimpleFontData*,
+    FontFallbackPriority fallbackPriority)
 {
+    if (fallbackPriority == FontFallbackPriority::EmojiEmoji) {
+        // FIXME crbug.com/591346: We're overriding the fallback character here
+        // with the FAMILY emoji in the hope to find a suitable emoji font.
+        // This should be improved by supporting fallback for character
+        // sequences like DIGIT ONE + COMBINING keycap etc.
+        c = familyCharacter;
+    }
+
     // First try the specified font with standard style & weight.
-    if (fontDescription.style() == FontStyleItalic
-        || fontDescription.weight() >= FontWeight600) {
+    if (fallbackPriority != FontFallbackPriority::EmojiEmoji
+        && (fontDescription.style() == FontStyleItalic
+        || fontDescription.weight() >= FontWeight600)) {
         RefPtr<SimpleFontData> fontData = fallbackOnStandardFontStyle(
             fontDescription, c);
         if (fontData)
             return fontData;
     }
 
     FontCache::PlatformFallbackFont fallbackFont;
     FontCache::getFontForCharacter(c, fontDescription.locale().ascii().data(), &fallbackFont);
     if (fallbackFont.name.isEmpty())
         return nullptr;
@@ skipping 25 matching lines @@
         return nullptr;
     FontPlatformData platformData = FontPlatformData(*substitutePlatformData);
     platformData.setSyntheticBold(shouldSetSyntheticBold);
     platformData.setSyntheticItalic(shouldSetSyntheticItalic);
     return fontDataFromFontPlatformData(&platformData, DoNotRetain);
 }
 
 #endif // !OS(ANDROID)
 
 } // namespace blink