cc: Avoid expensive RenderingStats collection.

cc/picture_pile_impl.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/picture_pile_impl.h"
 #include "cc/region.h"
 #include "cc/rendering_stats.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "third_party/skia/include/core/SkSize.h"
@@ skipping 47 matching lines @@
 }
 
 void PicturePileImpl::Raster(
     SkCanvas* canvas,
     gfx::Rect content_rect,
     float contents_scale,
     RenderingStats* stats) {
 
   DCHECK(contents_scale >= min_contents_scale_);
 
-  base::TimeTicks rasterizeBeginTime = base::TimeTicks::Now();
+  base::TimeTicks rasterize_begin_time;
+  if (stats)
+    rasterize_begin_time = base::TimeTicks::Now();
 
   canvas->save();
   canvas->translate(-content_rect.x(), -content_rect.y());
   canvas->clipRect(gfx::RectToSkRect(content_rect));
 
   gfx::Rect layer_rect = gfx::ToEnclosingRect(
       gfx::ScaleRect(content_rect, 1.f / contents_scale));
 
   Region unclipped(content_rect);
   for (TilingData::Iterator tile_iter(&tiling_, layer_rect);
@@ skipping 26 matching lines @@
       } else {
         (*i)->Raster(canvas, content_clip, contents_scale);
       }
 
       // Don't allow pictures underneath to draw where this picture did.
       canvas->clipRect(
           gfx::RectToSkRect(content_clip),
           SkRegion::kDifference_Op);
       unclipped.Subtract(content_clip);
 
-      stats->totalPixelsRasterized +=
-          content_clip.width() * content_clip.height();
+      if (stats)
+        stats->totalPixelsRasterized +=
+            content_clip.width() * content_clip.height();
     }
   }
   canvas->restore();
 
-  stats->totalRasterizeTime += base::TimeTicks::Now() - rasterizeBeginTime;
+  if (stats)
+    stats->totalRasterizeTime += base::TimeTicks::Now() - rasterize_begin_time;
 }
 
 void PicturePileImpl::GatherPixelRefs(
     gfx::Rect content_rect,
     float contents_scale,
     std::list<skia::LazyPixelRef*>& pixel_refs) {
   std::list<skia::LazyPixelRef*> result;
 
   gfx::Rect layer_rect = gfx::ToEnclosingRect(
       gfx::ScaleRect(content_rect, 1.f / contents_scale));
@@ skipping 33 matching lines @@
       SkPicture::kUsePathBoundsForClip_RecordingFlag);
 
   RenderingStats stats;
   Raster(canvas, layer_rect, 1.0, &stats);
   picture->endRecording();
 
   return picture;
 }
 
 }  // namespace cc