cc: Skip analysis for narrow layers.

cc/resources/tile_manager.cc

Index: cc/resources/tile_manager.cc
diff --git a/cc/resources/tile_manager.cc b/cc/resources/tile_manager.cc
index 8dc9c29ff0ae4527fc343c60bf58bf7b88a6092f..6ff314757b1257710ae9c624b4910335f57b8b88 100644
--- a/cc/resources/tile_manager.cc
+++ b/cc/resources/tile_manager.cc
@@ -32,6 +32,9 @@ namespace {
 // a tile is of solid color.
 const bool kUseColorEstimator = true;
 
+// Minimum width/height of a pile that would require analysis for tiles.
+const int kMinDimensionsForAnalysis = 256;
+
 class DisableLCDTextFilter : public SkDrawFilter {
  public:
   // SkDrawFilter interface.
@@ -1163,7 +1166,18 @@ scoped_refptr<internal::RasterWorkerPoolTask> TileManager::CreateRasterTask(
   // It is drawn directly as a solid-color quad saving raster and upload cost.
   // The analysis step is however expensive and is not justified when doing
   // gpu rasterization where there is no upload.
-  bool analyze_picture = !tile->use_gpu_rasterization();
+  //
+  // Additionally, we do not want to do the analysis if the layer that produced
+  // this tile is narrow, since more likely than not the tile would not be
+  // solid. We use the picture pile size as a proxy for layer size, since it
+  // represents the recorded (and thus rasterizable) content.
+  // Note that this last optimization is a heuristic that ensures that we don't
+  // spend too much time analyzing tiles on a multitude of small layers, as it
+  // is likely that these layers have some non-solid content.
+  gfx::Size pile_size = tile->picture_pile()->size();
+  bool analyze_picture = !tile->use_gpu_rasterization() &&
+                         std::min(pile_size.width(), pile_size.height()) >=
+                             kMinDimensionsForAnalysis;
 
   return make_scoped_refptr(new RasterWorkerPoolTaskImpl(
       const_resource,