Add keyboard handler for mime-handler-view.

BUG=411753
Test=With mime handler view turned on, click on a PDF to
focus the plugin, now send some keyboard event, like CTRL+L.
See the keyboard event work, i.e. the chrome address bar gets focus.

Review URL: https://codereview.chromium.org/557523002

Cr-Commit-Position: refs/heads/master@{#293868}

extensions/browser/guest_view/mime_handler_view/mime_handler_view_guest.cc

@@ -94,4 +94,20 @@ void MimeHandlerViewGuest::DidAttachToEmbedder() {
       std::string());
 }
 
+void MimeHandlerViewGuest::HandleKeyboardEvent(
+    WebContents* source,
+    const content::NativeWebKeyboardEvent& event) {
+  if (!attached())
+    return;
+
+  // Send the keyboard events back to the embedder to reprocess them.
+  // TODO(fsamuel): This introduces the possibility of out-of-order keyboard
+  // events because the guest may be arbitrarily delayed when responding to
+  // keyboard events. In that time, the embedder may have received and processed
+  // additional key events. This needs to be fixed as soon as possible.
+  // See http://crbug.com/229882.
+  embedder_web_contents()->GetDelegate()->HandleKeyboardEvent(web_contents(),
+                                                              event);
+}
+
 }  // namespace extensions

extensions/browser/guest_view/mime_handler_view/mime_handler_view_guest.h

@@ -26,6 +26,11 @@ class MimeHandlerViewGuest : public GuestView<MimeHandlerViewGuest> {
       const WebContentsCreatedCallback& callback) OVERRIDE;
   virtual void DidAttachToEmbedder() OVERRIDE;
 
+  // WebContentsDelegate implementation.
+  virtual void HandleKeyboardEvent(
+      content::WebContents* source,
+      const content::NativeWebKeyboardEvent& event) OVERRIDE;
+
  private:
   MimeHandlerViewGuest(content::BrowserContext* browser_context,
                        int guest_instance_id);