Implement on demand quad rasterization for PicturePiles.

cc/debug/debug_colors.cc

Index: cc/debug/debug_colors.cc
diff --git a/cc/debug/debug_colors.cc b/cc/debug/debug_colors.cc
index cc43480ac58cc9882a2badb4cbc48443feb0f469..01e72bb2cf26744edfe2ee9bec9885f49ffbf4f9 100644
--- a/cc/debug/debug_colors.cc
+++ b/cc/debug/debug_colors.cc
@@ -128,6 +128,10 @@ int DebugColors::SolidColorTileBorderWidth(const LayerTreeImpl* tree_impl) {
   return Scale(1, tree_impl);
 }
 
+// Picture tile borders are dark grey.
+SkColor DebugColors::PictureTileBorderColor() { return SkColorSetARGB(64, 64, 64, 0); }
+int DebugColors::PictureTileBorderWidth(const LayerTreeImpl* tree_impl) { return Scale(1, tree_impl); }
+
 // ======= Checkerboard colors =======
 
 // Non-debug checkerboards are grey.