Added NULL check in WebContentsViewAura when commencing a drag.

content/browser/web_contents/web_contents_view_aura.cc

 // Copyright (c) 2012 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 "content/browser/web_contents/web_contents_view_aura.h"
 
 #include "base/auto_reset.h"
 #include "base/command_line.h"
 #include "base/file_util.h"
 #include "base/metrics/histogram.h"
@@ skipping 1475 matching lines @@
 // WebContentsViewAura, aura::client::DragDropDelegate implementation:
 
 void WebContentsViewAura::OnDragEntered(const ui::DropTargetEvent& event) {
   current_rvh_for_drag_ = web_contents_->GetRenderViewHost();
   current_drop_data_.reset(new DropData());
 
   PrepareDropData(current_drop_data_.get(), event.data());
   blink::WebDragOperationsMask op = ConvertToWeb(event.source_operations());
 
   // Give the delegate an opportunity to cancel the drag.
-  if (!web_contents_->GetDelegate()->CanDragEnter(web_contents_,
-                                                  *current_drop_data_.get(),
-                                                  op)) {
+  if (web_contents_->GetDelegate() &&
+      !web_contents_->GetDelegate()->CanDragEnter(
+          web_contents_, *current_drop_data_.get(), op)) {
     current_drop_data_.reset(NULL);
     return;
   }
 
   if (drag_dest_delegate_)
     drag_dest_delegate_->DragInitialize(web_contents_);
 
   gfx::Point screen_pt =
       gfx::Screen::GetScreenFor(GetNativeView())->GetCursorScreenPoint();
   web_contents_->GetRenderViewHost()->DragTargetDragEnter(
@@ skipping 99 matching lines @@
   if (visible) {
     if (!web_contents_->should_normally_be_visible())
       web_contents_->WasShown();
   } else {
     if (web_contents_->should_normally_be_visible())
       web_contents_->WasHidden();
   }
 }
 
 }  // namespace content