Ignore certain messages in plugin broker process if they are not sent by the

content/browser/frame_host/render_frame_message_filter.cc

Index: content/browser/frame_host/render_frame_message_filter.cc
diff --git a/content/browser/frame_host/render_frame_message_filter.cc b/content/browser/frame_host/render_frame_message_filter.cc
index 98bd0fd5e3783c7150b678adff464706a4864953..bbffcca4fa9f4493e66edf629184e64e6b840f54 100644
--- a/content/browser/frame_host/render_frame_message_filter.cc
+++ b/content/browser/frame_host/render_frame_message_filter.cc
@@ -122,6 +122,9 @@ class RenderFrameMessageFilter::OpenChannelToPpapiBrokerCallback
 
   void GetPpapiChannelInfo(base::ProcessHandle* renderer_handle,
                            int* renderer_id) override {
+    // base::kNullProcessHandle indicates that the channel will be used by the
+    // browser itself. Make sure we never output that value here.
+    CHECK_NE(base::kNullProcessHandle, filter_->PeerHandle());
     *renderer_handle = filter_->PeerHandle();
     *renderer_id = filter_->render_process_id_;
   }
@@ -155,6 +158,9 @@ class RenderFrameMessageFilter::OpenChannelToPpapiPluginCallback
 
   void GetPpapiChannelInfo(base::ProcessHandle* renderer_handle,
                            int* renderer_id) override {
+    // base::kNullProcessHandle indicates that the channel will be used by the
+    // browser itself. Make sure we never output that value here.
+    CHECK_NE(base::kNullProcessHandle, filter()->PeerHandle());
     *renderer_handle = filter()->PeerHandle();
     *renderer_id = filter()->render_process_id_;
   }