detach blur result texture when it is the same texture used to render path mask

src/gpu/SkGpuDevice.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkGpuDevice.h"
 
 #include "effects/GrTextureDomainEffect.h"
@@ skipping 933 matching lines @@
                 return;
             }
 
             GrAutoScratchTexture mask;
 
             if (create_mask_GPU(fContext, maskRect, *devPathPtr, stroke,
                                 grPaint.isAntiAlias(), &mask)) {
                 GrTexture* filtered;
 
                 if (paint.getMaskFilter()->filterMaskGPU(mask.texture(), maskRect, &filtered, true)) {
+                    // filterMaskGPU gives us ownership of a ref to the result
                     SkAutoTUnref<GrTexture> atu(filtered);
 
+                    // If the scratch texture that we used as the filter src also holds the filter
+                    // result then we must detach so that this texture isn't recycled for a later
+                    // draw.
+                    if (filtered == mask.texture()) {
+                        mask.detach();
+                        filtered->unref(); // detach transfers GrAutoScratchTexture's ref to us.
+                    }
+
                     if (draw_mask(fContext, maskRect, &grPaint, filtered)) {
                         // This path is completely drawn
                         return;
                     }
                 }
             }
         }
 
         // draw the mask on the CPU - this is a fallthrough path in case the
         // GPU path fails
@@ skipping 876 matching lines @@
                          GrTexture* texture,
                          bool needClear)
     : SkBitmapDevice(make_bitmap(context, texture->asRenderTarget())) {
 
     SkASSERT(texture && texture->asRenderTarget());
     // This constructor is called from onCreateCompatibleDevice. It has locked the RT in the texture
     // cache. We pass true for the third argument so that it will get unlocked.
     this->initFromRenderTarget(context, texture->asRenderTarget(), true);
     fNeedClear = needClear;
 }