discard scratch render targets when they are recycled.

src/gpu/GrContext.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 "GrContext.h"
 
@@ skipping 455 matching lines @@
             uint32_t scratchFlags = 0;
             if (calledDuringFlush) {
                 scratchFlags = GrResourceCache2::kRequireNoPendingIO_ScratchFlag;
             } else  if (!(desc->fFlags & kRenderTarget_GrSurfaceFlag)) {
                 // If it is not a render target then it will most likely be populated by
                 // writePixels() which will trigger a flush if the texture has pending IO.
                 scratchFlags = GrResourceCache2::kPreferNoPendingIO_ScratchFlag;
             }
             GrGpuResource* resource = fResourceCache2->findAndRefScratchResource(key, scratchFlags);
             if (resource) {
-                return static_cast<GrSurface*>(resource)->asTexture();
+                GrSurface* surface = static_cast<GrSurface*>(resource);
+                GrRenderTarget* rt = surface->asRenderTarget();
+                if (rt && fGpu->caps()->discardRenderTargetSupport()) {
+                    rt->discard();
+                }
+                return surface->asTexture();
             }
 
             if (kExact_ScratchTexMatch == match) {
                 break;
             }
             // We had a cache miss and we are in approx mode, relax the fit of the flags.
 
             // We no longer try to reuse textures that were previously used as render targets in
             // situations where no RT is needed; doing otherwise can confuse the video driver and
             // cause significant performance problems in some cases.
@@ skipping 1301 matching lines @@
     fResourceCache2->printStats();
 }
 #endif
 
 #if GR_GPU_STATS
 const GrContext::GPUStats* GrContext::gpuStats() const {
     return fGpu->gpuStats();
 }
 #endif