Implement on demand quad rasterization for PicturePiles.

cc/debug_colors.cc

Index: cc/debug_colors.cc
diff --git a/cc/debug_colors.cc b/cc/debug_colors.cc
index 8c998fe41ef9bf2bc8ff8520ea0f78fa91c2ff12..a79ea4a2366c9422f941f57bd541d8dffebd22c4 100644
--- a/cc/debug_colors.cc
+++ b/cc/debug_colors.cc
@@ -72,6 +72,10 @@ int DebugColors::CulledTileBorderWidth(const LayerTreeImpl* tree_impl) { return
 SkColor DebugColors::SolidColorTileBorderColor() { return SkColorSetARGB(128, 128, 128, 128); }
 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.