Revert of Fix bug in plot locking system

src/gpu/GrLayerCache.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrLayerCache_DEFINED
 #define GrLayerCache_DEFINED
 
@@ skipping 213 matching lines @@
 
     SkTDynamicHash<GrCachedLayer, GrCachedLayer::Key> fLayerHash;
 
     SkMessageBus<GrPictureDeletedMessage>::Inbox fPictDeletionInbox;
 
     SkAutoTUnref<SkPicture::DeletionListener> fDeletionListener;
 
     // This implements a plot-centric locking mechanism (since the atlas
     // backing texture is always locked). Each layer that is locked (i.e.,
     // needed for the current rendering) in a plot increments the plot lock
-    // count for that plot for each time it is used. Similarly, once a 
-    // rendering is complete all the layers used in it decrement the lock
-    // count for the used plots. Plots with a 0 lock count are open for 
-    // recycling/purging.
+    // count for that plot. Similarly, once a rendering is complete all the
+    // layers used in it decrement the lock count for the used plots.
+    // Plots with a 0 lock count are open for recycling/purging.
     int fPlotLocks[kNumPlotsX * kNumPlotsY];
 
     void initAtlas();
     GrCachedLayer* createLayer(uint32_t pictureID, int start, int stop, 
                                const SkMatrix& ctm, const SkPaint* paint);
 
     void purgeAll();
 
     // Remove all the layers (and unlock any resources) associated with 'pictureID'
     void purge(uint32_t pictureID);
 
     static bool PlausiblyAtlasable(int width, int height) {
         return width <= kPlotWidth && height <= kPlotHeight;
     }
 
     void purgePlot(GrPlot* plot);
 
     // Try to find a purgeable plot and clear it out. Return true if a plot
     // was purged; false otherwise.
     bool purgePlot();
 
-    void incPlotLock(int plotIdx) { ++fPlotLocks[plotIdx]; }
-    void decPlotLock(int plotIdx) {
-        SkASSERT(fPlotLocks[plotIdx] > 0);
-        --fPlotLocks[plotIdx];
-    }
-
     // for testing
     friend class TestingAccess;
     int numLayers() const { return fLayerHash.count(); }
 };
 
 #endif