Listen to didReceiveResponse() to get the response in WebViewPlugin.

components/plugins/renderer/webview_plugin.h

Index: components/plugins/renderer/webview_plugin.h
diff --git a/components/plugins/renderer/webview_plugin.h b/components/plugins/renderer/webview_plugin.h
index f73df622784cc8fee3c832abb10030893197a951..054294c72b2ede97c1f56f1c822aafed3056a231 100644
--- a/components/plugins/renderer/webview_plugin.h
+++ b/components/plugins/renderer/webview_plugin.h
@@ -108,7 +108,7 @@ class WebViewPlugin : public blink::WebPlugin,
       const blink::WebInputEvent& event,
       blink::WebCursorInfo& cursor_info) override;
 
-  void didReceiveResponse(const blink::WebURLResponse& response) override {}
+  void didReceiveResponse(const blink::WebURLResponse& response) override;
   void didReceiveData(const char* data, int data_length) override;
   void didFinishLoading() override;
   void didFailLoading(const blink::WebURLError& error) override;
@@ -169,6 +169,7 @@ class WebViewPlugin : public blink::WebPlugin,
   blink::WebFrame* web_frame_;
   gfx::Rect rect_;
 
+  blink::WebURLResponse response_;
   std::list<std::string> data_;
   std::unique_ptr<blink::WebURLError> error_;
   blink::WebString old_title_;