Add a flag to disable partial raster in renderer

cc/base/switches.cc

Index: cc/base/switches.cc
diff --git a/cc/base/switches.cc b/cc/base/switches.cc
index 0db15030d5b5a661a16398c420e79b4ad6072732..a906c65c1b789c82f13ecbbb483704a3a961de31 100644
--- a/cc/base/switches.cc
+++ b/cc/base/switches.cc
@@ -44,6 +44,9 @@ const char kStrictLayerPropertyChangeChecking[] =
 const char kEnablePropertyTreeVerification[] =
     "enable-property-tree-verification";
 
+// Enables re-use of tile resources, allowing rasterization of dirty areas only.
+const char kEnablePartialRaster[] = "enable-partial-raster";
+
 // Disable partial swap which is needed for some OpenGL drivers / emulators.
 const char kUIDisablePartialSwap[] = "ui-disable-partial-swap";