Chromecast: add platform hooks to inject browser/renderer message filters.

chromecast/renderer/cast_content_renderer_client_simple.cc

Index: chromecast/renderer/cast_content_renderer_client_simple.cc
diff --git a/chromecast/renderer/cast_content_renderer_client_simple.cc b/chromecast/renderer/cast_content_renderer_client_simple.cc
index e8d40c6dfbb4a34ccd2406067b6bccb0736e91f7..5ad4fccb261cbdcd6fd15da33f6dbe1cdd5b6a16 100644
--- a/chromecast/renderer/cast_content_renderer_client_simple.cc
+++ b/chromecast/renderer/cast_content_renderer_client_simple.cc
@@ -4,11 +4,18 @@
 
 #include "chromecast/renderer/cast_content_renderer_client.h"
 
+#include "ipc/message_filter.h"
+
 namespace chromecast {
 namespace shell {
 
 void PlatformAddRendererNativeBindings(blink::WebLocalFrame* frame) {
 }
 
+std::vector<scoped_refptr<IPC::MessageFilter>>
+CastContentRendererClient::PlatformGetRendererMessageFilters() {
+  return std::vector<scoped_refptr<IPC::MessageFilter>>();
+}
+
 }  // namespace shell
 }  // namespace chromecast