Avoid creating full screen clear batches when there is already one in the queue.

src/gpu/GrDrawContext.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrBatchTest.h"
 #include "GrColor.h"
 #include "GrDrawContext.h"
@@ skipping 215 matching lines @@
         }
 
         GrPaint paint;
         paint.setColor4f(GrColor4f::FromGrColor(color));
         paint.setXPFactory(GrPorterDuffXPFactory::Make(SkXfermode::kSrc_Mode));
 
         this->drawRect(GrNoClip(), paint, SkMatrix::I(), SkRect::Make(*rect));
     } else if (isFull) {
         this->getDrawTarget()->fullClear(this->accessRenderTarget(), color);
     } else {
-        sk_sp<GrBatch> batch = GrClearBatch::Make(*rect, color, this->accessRenderTarget());
+        sk_sp<GrBatch> batch(GrClearBatch::Make(*rect, color, this->accessRenderTarget()));
         this->getDrawTarget()->addBatch(std::move(batch));
     }
 }
 
 
 void GrDrawContext::drawPaint(const GrClip& clip,
                               const GrPaint& origPaint,
                               const SkMatrix& viewMatrix) {
     ASSERT_SINGLE_OWNER
     RETURN_IF_ABANDONED
@@ skipping 1060 matching lines @@
 
 void GrDrawContext::drawBatch(const GrPipelineBuilder& pipelineBuilder, const GrClip& clip,
                               GrDrawBatch* batch) {
     ASSERT_SINGLE_OWNER
     RETURN_IF_ABANDONED
     SkDEBUGCODE(this->validate();)
     GR_AUDIT_TRAIL_AUTO_FRAME(fAuditTrail, "GrDrawContext::drawBatch");
 
     this->getDrawTarget()->drawBatch(pipelineBuilder, this, clip, batch);
 }