Implemented explicit resizing from guestview.

extensions/common/guest_view/guest_view_constants.cc

Index: extensions/common/guest_view/guest_view_constants.cc
diff --git a/extensions/common/guest_view/guest_view_constants.cc b/extensions/common/guest_view/guest_view_constants.cc
index 465d6baaa1c3eb4e29a3391e9cf0302d91c68c7f..3ef82a6b327bd0a3d20512164aa93e0816f9c673 100644
--- a/extensions/common/guest_view/guest_view_constants.cc
+++ b/extensions/common/guest_view/guest_view_constants.cc
@@ -6,12 +6,14 @@
 
 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";
@@ -26,5 +28,7 @@ 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