cc: Implement tiling iterator based on pyramid sequence.

cc/base/switches.cc

Index: cc/base/switches.cc
diff --git a/cc/base/switches.cc b/cc/base/switches.cc
index 3d2fa44a324be9f96c7910d2ce83025033380eab..9ce00fc02f3526a3d36ce839c58326eacb56e89c 100644
--- a/cc/base/switches.cc
+++ b/cc/base/switches.cc
@@ -52,6 +52,11 @@ const char kEnableColorCorrectRendering[] = "enable-color-correct-rendering";
 // Enables the GPU benchmarking extension
 const char kEnableGpuBenchmarking[] = "enable-gpu-benchmarking";
 
+// Enables the different tiling iterator. For better iteration order of odd
+// sized tiles, i.e. tiles not having aspect ratio 1, specify
+// "--tiling-iterator=pyramid-sequence".
+const char kTilingIterator[] = "tiling-iterator";
+
 // Renders a border around compositor layers to help debug and study
 // layer compositing.
 const char kShowCompositedLayerBorders[] = "show-composited-layer-borders";