cc: Add tile-free software compositing mode.

cc/resources/tile_manager.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 "cc/resources/tile_manager.h"
 
 #include <algorithm>
 #include <string>
 
 #include "base/bind.h"
@@ skipping 907 matching lines @@
 
   DCHECK(picture_pile);
   DCHECK(buffer);
 
   SkBitmap bitmap;
   bitmap.setConfig(SkBitmap::kARGB_8888_Config, rect.width(), rect.height());
   bitmap.setPixels(buffer);
   SkDevice device(bitmap);
   SkCanvas canvas(&device);
 
+#ifndef NDEBUG
+  // Any non-painted areas will be left in this color.
+  canvas->clear(DebugColors::NonPaintedFillColor());
+#endif  // NDEBUG
+
   if (stats_instrumentation->record_rendering_stats()) {
     PicturePileImpl::RasterStats raster_stats;
     picture_pile->Raster(&canvas, rect, contents_scale, &raster_stats);
     stats_instrumentation->AddRaster(raster_stats.total_rasterize_time,
                                      raster_stats.best_rasterize_time,
                                      raster_stats.total_pixels_rasterized,
                                      metadata.is_tile_in_pending_tree_now_bin);
 
     HISTOGRAM_CUSTOM_COUNTS("Renderer4.PictureRasterTimeUS",
                             raster_stats.total_rasterize_time.InMicroseconds(),
@@ skipping 92 matching lines @@
     skia::LazyPixelRef* pixel_ref,
     RenderingStatsInstrumentation* stats_instrumentation) {
   TRACE_EVENT0("cc", "TileManager::RunImageDecodeTask");
   base::TimeTicks start_time = stats_instrumentation->StartRecording();
   pixel_ref->Decode();
   base::TimeDelta duration = stats_instrumentation->EndRecording(start_time);
   stats_instrumentation->AddDeferredImageDecode(duration);
 }
 
 }  // namespace cc