Relanding this with fixes to the mac dbg builder

ppapi/thunk/ppb_image_data_api.h

Index: ppapi/thunk/ppb_image_data_api.h
===================================================================
--- ppapi/thunk/ppb_image_data_api.h	(revision 118405)
+++ ppapi/thunk/ppb_image_data_api.h	(working copy)
@@ -8,6 +8,10 @@
 #include "ppapi/c/pp_bool.h"
 #include "ppapi/c/ppb_image_data.h"
 
+namespace skia {
+class PlatformCanvas;
+}
+
 namespace ppapi {
 namespace thunk {
 
@@ -21,6 +25,9 @@
 
   // Trusted inteface.
   virtual int32_t GetSharedMemory(int* handle, uint32_t* byte_count) = 0;
+
+  // The canvas will be NULL if the image is not mapped.
+  virtual skia::PlatformCanvas* GetPlatformCanvas() = 0;
 };
 
 }  // namespace thunk