cc: Avoid expensive RenderingStats collection.

cc/picture.cc

 // Copyright 2012 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 "base/debug/trace_event.h"
 #include "cc/content_layer_client.h"
 #include "cc/picture.h"
 #include "cc/rendering_stats.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "third_party/skia/include/core/SkData.h"
@@ skipping 32 matching lines @@
 
 scoped_refptr<Picture> Picture::Clone() const {
   // SkPicture is not thread-safe to rasterize with, so return a thread-safe
   // clone of it.
   DCHECK(picture_);
   skia::RefPtr<SkPicture> clone = skia::AdoptRef(picture_->clone());
   return make_scoped_refptr(new Picture(clone, layer_rect_, opaque_rect_));
 }
 
 void Picture::Record(ContentLayerClient* painter,
-                     RenderingStats& stats) {
+                     RenderingStats* stats) {
   TRACE_EVENT2("cc", "Picture::Record",
                "width", layer_rect_.width(), "height", layer_rect_.height());
 
   // Record() should only be called once.
   DCHECK(!picture_);
   picture_ = skia::AdoptRef(new SkTileGridPicture(
       tileGridSize, tileGridSize, layer_rect_.width(), layer_rect_.height()));
 
   SkCanvas* canvas = picture_->beginRecording(
       layer_rect_.width(),
       layer_rect_.height(),
       SkPicture::kUsePathBoundsForClip_RecordingFlag |
       SkPicture::kOptimizeForClippedPlayback_RecordingFlag);
 
   canvas->save();
   canvas->translate(SkFloatToScalar(-layer_rect_.x()),
                     SkFloatToScalar(-layer_rect_.y()));
 
   SkPaint paint;
   paint.setAntiAlias(false);
   paint.setXfermodeMode(SkXfermode::kClear_Mode);
   SkRect layer_skrect = SkRect::MakeXYWH(layer_rect_.x(),
                                          layer_rect_.y(),
                                          layer_rect_.width(),
                                          layer_rect_.height());
   canvas->clipRect(layer_skrect);
   canvas->drawRect(layer_skrect, paint);
 
   gfx::RectF opaque_layer_rect;
-  base::TimeTicks beginPaintTime = base::TimeTicks::Now();
+  base::TimeTicks begin_paint_time;
+  if (stats)
+    begin_paint_time = base::TimeTicks::Now();
   painter->paintContents(canvas, layer_rect_, opaque_layer_rect);
-  stats.totalPaintTime += base::TimeTicks::Now() - beginPaintTime;
-  stats.totalPixelsPainted += layer_rect_.width() *
-                              layer_rect_.height();
+  if (stats) {
+    stats->totalPaintTime += base::TimeTicks::Now() - begin_paint_time;
+    stats->totalPixelsPainted +=
+        layer_rect_.width() * layer_rect_.height();
+  }
 
   canvas->restore();
   picture_->endRecording();
 
   opaque_rect_ = gfx::ToEnclosedRect(opaque_layer_rect);
 }
 
 void Picture::Raster(
     SkCanvas* canvas,
     gfx::Rect content_rect,
@@ skipping 32 matching lines @@
     if (*refs && (*refs)->getURI() && !strncmp(
         (*refs)->getURI(), labelLazyDecoded, 4)) {
       pixel_ref_list.push_back(static_cast<skia::LazyPixelRef*>(*refs));
     }
     refs++;
   }
   pixel_refs->unref();
 }
 
 }  // namespace cc