Add FontCache API for retrieving prioritized fallback fonts

third_party/WebKit/Source/platform/fonts/FontCacheTest.cpp

Index: third_party/WebKit/Source/platform/fonts/FontCacheTest.cpp
diff --git a/third_party/WebKit/Source/platform/fonts/FontCacheTest.cpp b/third_party/WebKit/Source/platform/fonts/FontCacheTest.cpp
index c97c74561cf132ac33cc553a3cb8dab64b713050..0de438dc108fb2e151d3977a8e2ad23db94e7e22 100644
--- a/third_party/WebKit/Source/platform/fonts/FontCacheTest.cpp
+++ b/third_party/WebKit/Source/platform/fonts/FontCacheTest.cpp
@@ -35,4 +35,27 @@ TEST(FontCache, getLastResortFallbackFont)
     EXPECT_TRUE(fontData);
 }
 
+TEST(FontCache, availablePriorityFallbackFonts)
+{
+    FontCache* fontCache = FontCache::fontCache();
+    ASSERT_TRUE(fontCache);
+
+    EmptyPlatform platform;
+
+    FontDescription fontDescription;
+    fontDescription.setGenericFamily(FontDescription::StandardFamily);
+
+    for (FontFallbackPriority fallbackPriority :
+        { FontFallbackPriority::Symbols,
+            FontFallbackPriority::Math,
+            FontFallbackPriority::EmojiText,
+            FontFallbackPriority::EmojiEmoji }) {
+
+        const Vector<AtomicString> availableFallbackPriorityFonts =
+            fontCache->fontListForFallbackPriority(fontDescription,
+            fallbackPriority);
+        EXPECT_GE(availableFallbackPriorityFonts.size(), 1u);
+    }
+}
+
 } // namespace blink