Defer glClear to just before draw call

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 "GrBitmapTextContext.h"
@@ skipping 44 matching lines @@
         } while (0)
 #else
     #define CHECK_SHOULD_DRAW(draw) this->prepareDraw(draw)
 #endif
 
 // This constant represents the screen alignment criterion in texels for
 // requiring texture domain clamping to prevent color bleeding when drawing
 // a sub region of a larger source image.
 #define COLOR_BLEED_TOLERANCE 0.001f
 
+// Do deferred clear just before any draw call
 #define DO_DEFERRED_CLEAR()             \
     do {                                \
         if (fNeedClear) {               \
             this->clearAll();           \
         }                               \
     } while (false)                     \
 
 ///////////////////////////////////////////////////////////////////////////////
 
 #define CHECK_FOR_ANNOTATION(paint) \
@@ skipping 219 matching lines @@
     SkASSERT(fClipStack.get());
 
     SkASSERT(draw.fClipStack && draw.fClipStack == fClipStack);
 
     fClip.setClipStack(fClipStack, &this->getOrigin());
 
     DO_DEFERRED_CLEAR();
 }
 
 GrRenderTarget* SkGpuDevice::accessRenderTarget() {
-    DO_DEFERRED_CLEAR();
     return fRenderTarget;
 }
 
 void SkGpuDevice::clearAll() {
     GrColor color = 0;
     GR_CREATE_TRACE_MARKER_CONTEXT("SkGpuDevice::clearAll", fContext);
     SkIRect rect = SkIRect::MakeWH(this->width(), this->height());
     fContext->clear(&rect, color, true, fRenderTarget);
     fNeedClear = false;
 }
@@ skipping 1718 matching lines @@
 #endif
 }
 
 SkImageFilter::Cache* SkGpuDevice::getImageFilterCache() {
     // We always return a transient cache, so it is freed after each
     // filter traversal.
     return SkImageFilter::Cache::Create(kDefaultImageFilterCacheSize);
 }
 
 #endif