add clip to PictureRenderer to better mimic Chromium's rendering method

tools/PictureRenderer.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "PictureRenderer.h"
 #include "picture_utils.h"
 #include "SamplePipeControllers.h"
@@ skipping 600 matching lines @@
  */
 static void draw_tile_to_canvas(SkCanvas* canvas,
                                 const SkIRect& tileRect,
                                 const SkPicture* picture) {
     int saveCount = canvas->save();
     // Translate so that we draw the correct portion of the picture.
     // Perform a postTranslate so that the scaleFactor does not interfere with the positioning.
     SkMatrix mat(canvas->getTotalMatrix());
     mat.postTranslate(-SkIntToScalar(tileRect.fLeft), -SkIntToScalar(tileRect.fTop));
     canvas->setMatrix(mat);
+    canvas->clipRect(SkRect::Make(tileRect));
     canvas->clear(SK_ColorTRANSPARENT); // Not every picture covers the entirety of every tile
     canvas->drawPicture(picture);
     canvas->restoreToCount(saveCount);
     canvas->flush();
 }
 
 ///////////////////////////////////////////////////////////////////////////////////////////////
 
 /**
  * Copies the entirety of the src bitmap (typically a tile) into a portion of the dst bitmap.
@@ skipping 222 matching lines @@
 PictureRenderer* CreateGatherPixelRefsRenderer(const GrContext::Options& opts) {
     return SkNEW_ARGS(GatherRenderer, (opts));
 }
 #else
 PictureRenderer* CreateGatherPixelRefsRenderer() {
     return SkNEW(GatherRenderer);
 }
 #endif
 
 } // namespace sk_tools