cc: Cull DrawingDisplayItems outside of the raster playback rect

cc/playback/drawing_display_item.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/playback/drawing_display_item.h"
 
 #include <string>
 
 #include "base/strings/stringprintf.h"
 #include "base/trace_event/trace_event_argument.h"
 #include "cc/debug/picture_debug_util.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "third_party/skia/include/core/SkMatrix.h"
 #include "third_party/skia/include/core/SkPicture.h"
 #include "third_party/skia/include/utils/SkPictureUtils.h"
+#include "ui/gfx/skia_util.h"
 
 namespace cc {
 
 DrawingDisplayItem::DrawingDisplayItem() {
 }
 
 DrawingDisplayItem::~DrawingDisplayItem() {
 }
 
 void DrawingDisplayItem::SetNew(skia::RefPtr<SkPicture> picture) {
   picture_ = picture.Pass();
   DisplayItem::SetNew(picture_->suitableForGpuRasterization(NULL),
                       picture_->approximateOpCount(),
                       SkPictureUtils::ApproximateBytesUsed(picture_.get()));
 }
 
 void DrawingDisplayItem::Raster(SkCanvas* canvas,
+                                const gfx::Rect& canvas_target_playback_rect,
                                 SkPicture::AbortCallback* callback) const {
+  // The canvas_playback_rect can be empty to signify no culling is desired.
+  if (!canvas_target_playback_rect.IsEmpty()) {
+    const SkMatrix& matrix = canvas->getTotalMatrix();
+    const SkRect& cull_rect = picture_->cullRect();
+    SkRect target_rect;
+    matrix.mapRect(&target_rect, cull_rect);
+    if (!target_rect.intersect(gfx::RectToSkRect(canvas_target_playback_rect)))
+      return;
+  }
+
   // SkPicture always does a wrapping save/restore on the canvas, so it is not
   // necessary here.
   if (callback)
     picture_->playback(canvas, callback);
   else
     canvas->drawPicture(picture_.get());
 }
 
 void DrawingDisplayItem::AsValueInto(
     base::trace_event::TracedValue* array) const {
   array->BeginDictionary();
   array->SetString("name", "DrawingDisplayItem");
   array->SetString(
       "cullRect",
       base::StringPrintf("[%f,%f,%f,%f]", picture_->cullRect().x(),
                          picture_->cullRect().y(), picture_->cullRect().width(),
                          picture_->cullRect().height()));
   std::string b64_picture;
   PictureDebugUtil::SerializeAsBase64(picture_.get(), &b64_picture);
   array->SetString("skp64", b64_picture);
   array->EndDictionary();
 }
 
 void DrawingDisplayItem::CloneTo(DrawingDisplayItem* item) const {
   item->SetNew(picture_);
 }
 
 }  // namespace cc