Mojo: Change how we handle invalid pointer arguments (at the system layer).

mojo/system/mapping_table.h

Index: mojo/system/mapping_table.h
diff --git a/mojo/system/mapping_table.h b/mojo/system/mapping_table.h
index 5268234b1fe3af2f15939ab097f99d6e00c3e6c9..e21d685b12214aaad670a27173c90b92c6bb67d4 100644
--- a/mojo/system/mapping_table.h
+++ b/mojo/system/mapping_table.h
@@ -39,7 +39,7 @@ class MOJO_SYSTEM_IMPL_EXPORT MappingTable {
   // Tries to add a mapping. (Takes ownership of the mapping in all cases; on
   // failure, it will be destroyed.)
   MojoResult AddMapping(scoped_ptr<RawSharedBufferMapping> mapping);
-  MojoResult RemoveMapping(void* address);
+  MojoResult RemoveMapping(uintptr_t address);
 
  private:
   friend bool internal::ShutdownCheckNoLeaks(Core*);