Remove deferred clear from SkGpuDevice

src/gpu/batches/GrClearBatch.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrClearBatch_DEFINED
 #define GrClearBatch_DEFINED
 
@@ skipping 22 matching lines @@
     SkString dumpInfo() const override {
         SkString string;
         string.printf("Color: 0x%08x, Rect [L: %d, T: %d, R: %d, B: %d], RT: %d",
                       fColor, fRect.fLeft, fRect.fTop, fRect.fRight, fRect.fBottom,
                       fRenderTarget.get()->getUniqueID());
         return string;
     }
 
 private:
     bool onCombineIfPossible(GrBatch* t, const GrCaps& caps) override {
-        // We could combine clears. TBD how much complexity to put here.
+        // This could be much more complicated. Currently we look at cases where the new clear
+        // contains the old clear, or when the new clear is a subset of the old clear and is the
+        // same color.
+        GrClearBatch* cb = t->cast<GrClearBatch>();
+        SkASSERT(cb->fRenderTarget == fRenderTarget);
+        if (cb->fRect.contains(fRect)) {
+            fRect = cb->fRect;
+            fBounds = cb->fBounds;
+            fColor = cb->fColor;
+            return true;
+        } else if (cb->fColor == fColor && fRect.contains(cb->fRect)) {
+            return true;
+        }
         return false;
     }
 
     void onPrepare(GrBatchFlushState*) override {}
 
     void onDraw(GrBatchFlushState* state) override {
         state->gpu()->clear(fRect, fColor, fRenderTarget.get());
     }
 
     SkIRect                                                 fRect;
@@ skipping 38 matching lines @@
     }
 
     SkIRect                                                 fRect;
     bool                                                    fInsideClip;
     GrPendingIOResource<GrRenderTarget, kWrite_GrIOType>    fRenderTarget;
 
     typedef GrBatch INHERITED;
 };
 
 #endif