Bug 1143575. Remove unused ImageContainer::ResetPaintCount. r=nical

--HG--
extra : commitid : HGiTU6g5Puk
extra : rebase_source : 5550d38a6d9a91e5be5885152885df37ddf3dfa5

gfx/layers/ImageContainer.h

@@ -468,15 +468,6 @@ public:
     return mPaintCount;
   }
 
-  /**
-   * Resets the paint count to zero.
-   * Can be called from any thread.
-   */
-  void ResetPaintCount() {
-    ReentrantMonitorAutoEnter mon(mReentrantMonitor);
-    mPaintCount = 0;
-  }
-
   /**
    * Increments mPaintCount if this is the first time aPainted has been
    * painted, and sets mPaintTime if the painted image is the current image.