Implemented explicit resizing from guestview.

extensions/common/guest_view/guest_view_constants.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "extensions/common/guest_view/guest_view_constants.h"
 
 namespace guestview {
 
-// Sizing Attributes.
+// Sizing attributes/parameters.
 const char kAttributeAutoSize[] = "autosize";
 const char kAttributeMaxHeight[] = "maxheight";
 const char kAttributeMaxWidth[] = "maxwidth";
 const char kAttributeMinHeight[] = "minheight";
 const char kAttributeMinWidth[] = "minwidth";
+const char kElementWidth[] = "elementWidth";
+const char kElementHeight[] = "elementHeight";
 
 // Parameters/properties on events.
 const char kIsTopLevel[] = "isTopLevel";
 const char kReason[] = "reason";
 const char kUrl[] = "url";
 const char kUserGesture[] = "userGesture";
 
 // Initialization parameters.
 const char kParameterApi[] = "api";
 const char kParameterInstanceId[] = "instanceId";
 
 // Other.
 const char kGuestViewManagerKeyName[] = "guest_view_manager";
 const int kInstanceIDNone = 0;
+const int kDefaultWidth = 300;
+const int kDefaultHeight = 300;
 
 }  // namespace guestview