bug 894798 - disable word-cache expiration timer on release builds. r=roc

gfx/thebes/gfxFont.cpp

@@ -1455,6 +1455,9 @@ gfxFontCache::gfxFontCache()
         obs->AddObserver(new Observer, "memory-pressure", false);
     }
 
+#ifndef RELEASE_BUILD
+    // Currently disabled for release builds, due to unexplained crashes
+    // during expiration; see bug 717175 & 894798.
     mWordCacheExpirationTimer = do_CreateInstance("@mozilla.org/timer;1");
     if (mWordCacheExpirationTimer) {
         mWordCacheExpirationTimer->
@@ -1462,6 +1465,7 @@ gfxFontCache::gfxFontCache()
                                  SHAPED_WORD_TIMEOUT_SECONDS * 1000,
                                  nsITimer::TYPE_REPEATING_SLACK);
     }
+#endif
 }
 
 gfxFontCache::~gfxFontCache()