Move host resource from the proxy to the shared_impl.

ppapi/proxy/mock_resource.cc

Index: ppapi/proxy/mock_resource.cc
diff --git a/ppapi/proxy/mock_resource.cc b/ppapi/proxy/mock_resource.cc
index 21e5381c9469f365396dbf30c0cad0dba429d08e..2f1a0b7cbba2e153f4a8a7037c65ff1acdf2b4b0 100644
--- a/ppapi/proxy/mock_resource.cc
+++ b/ppapi/proxy/mock_resource.cc
@@ -4,6 +4,8 @@
 
 #include "ppapi/proxy/mock_resource.h"
 
+using ppapi::HostResource;
+
 namespace pp {
 namespace proxy {
 
@@ -14,9 +16,5 @@ MockResource::MockResource(const HostResource& resource)
 MockResource::~MockResource() {
 }
 
-MockResource* MockResource::AsMockResource() {
-  return this;
-}
-
 }  // namespace proxy
 }  // namespace pp