Move host resource from the proxy to the shared_impl.

ppapi/proxy/mock_resource.h

Index: ppapi/proxy/mock_resource.h
diff --git a/ppapi/proxy/mock_resource.h b/ppapi/proxy/mock_resource.h
index 7e38be188030327d4f6ce33945237120f55ef9d0..dbad2f6074012d6b06e431e12f82ae766f1510e0 100644
--- a/ppapi/proxy/mock_resource.h
+++ b/ppapi/proxy/mock_resource.h
@@ -13,12 +13,9 @@ namespace proxy {
 
 class MockResource : public PluginResource {
  public:
-  MockResource(const HostResource& resource);
+  MockResource(const ppapi::HostResource& resource);
   virtual ~MockResource();
 
-  // Resource overrides.
-  virtual MockResource* AsMockResource();
-
  private:
   DISALLOW_COPY_AND_ASSIGN(MockResource);
 };