bug 727815 - flush shaped-word caches when font-shaping preferences are modified. r=roc

gfx/thebes/gfxPlatform.cpp

@@ -1358,11 +1358,19 @@ gfxPlatform::FontsPrefsChanged(const char *aPref)
 #ifdef MOZ_GRAPHITE
     } else if (!strcmp(GFX_PREF_GRAPHITE_SHAPING, aPref)) {
         mGraphiteShapingEnabled = UNINITIALIZED_VALUE;
-        gfxFontCache::GetCache()->AgeAllGenerations();
+        gfxFontCache *fontCache = gfxFontCache::GetCache();
+        if (fontCache) {
+            fontCache->AgeAllGenerations();
+            fontCache->FlushShapedWordCaches();
+        }
 #endif
     } else if (!strcmp(GFX_PREF_HARFBUZZ_SCRIPTS, aPref)) {
         mUseHarfBuzzScripts = UNINITIALIZED_VALUE;
-        gfxFontCache::GetCache()->AgeAllGenerations();
+        gfxFontCache *fontCache = gfxFontCache::GetCache();
+        if (fontCache) {
+            fontCache->AgeAllGenerations();
+            fontCache->FlushShapedWordCaches();
+        }
     } else if (!strcmp(BIDI_NUMERAL_PREF, aPref)) {
         mBidiNumeralOption = UNINITIALIZED_VALUE;
     }