Add context menu support (issue #509):

- Add new CefContextMenuHandler, CefContextMenuParams and CefMenuModel classes.
- Add cef_strings.grd and related infrastructure for supporting translation of CEF strings.
- Generate include/cef_pack_resources.h and include/cef_pack_strings.h files at build time that include all IDs used by CEF pack files.

git-svn-id: https://chromiumembedded.googlecode.com/svn/trunk@595 5089003a-bbd8-11dd-ad1f-f1f9622dbc98

include/cef_client.h

@@ -39,6 +39,7 @@
 #pragma once
 
 #include "include/cef_base.h"
+#include "include/cef_context_menu_handler.h"
 #include "include/cef_display_handler.h"
 #include "include/cef_geolocation_handler.h"
 #include "include/cef_jsdialog_handler.h"
@@ -103,6 +104,15 @@ class CefClient : public virtual CefBase {
     return NULL;
   }
 
+  ///
+  // Return the handler for context menus. If no handler is provided the default
+  // implementation will be used.
+  ///
+  /*--cef()--*/
+  virtual CefRefPtr<CefContextMenuHandler> GetContextMenuHandler() {
+    return NULL;
+  }
+
   ///
   // Called when a new message is received from a different process. Return true
   // if the message was handled or false otherwise. Do not keep a reference to