Enable external popup menu in Blimp, part 2/2.

blimp/engine/app/blimp_content_browser_client.h

Index: blimp/engine/app/blimp_content_browser_client.h
diff --git a/blimp/engine/app/blimp_content_browser_client.h b/blimp/engine/app/blimp_content_browser_client.h
index ab5e89578e5d1e634a3e13afc166cfe3a05ab1d5..c6ea5aaa93d2f8ca5d61dd6ad7c226d17de4504e 100644
--- a/blimp/engine/app/blimp_content_browser_client.h
+++ b/blimp/engine/app/blimp_content_browser_client.h
@@ -8,6 +8,10 @@
 #include "base/macros.h"
 #include "content/public/browser/content_browser_client.h"
 
+namespace content {
+class WebContentsViewDelegate;
+}
+
 namespace blimp {
 namespace engine {
 
@@ -30,6 +34,8 @@ class BlimpContentBrowserClient : public content::ContentBrowserClient {
                            content::WebPreferences* prefs) override;
   void RegisterRenderProcessMojoServices(
       content::ServiceRegistry* registry) override;
+  content::WebContentsViewDelegate* GetWebContentsViewDelegate(
+      content::WebContents* web_contents) override;
 
   BlimpBrowserContext* GetBrowserContext();