Try to track down the cause of the Drag&Drop crash seen in bug 12524....

chrome/browser/tab_contents/web_drag_source.cc

 // Copyright (c) 2006-2008 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.
 
 #if defined(OS_WIN)
 #include <atlbase.h>
 #include <atlapp.h>
 #include <atlmisc.h>
 #endif
 
@@ skipping 19 matching lines @@
 
 }  // namespace
 ///////////////////////////////////////////////////////////////////////////////
 // WebDragSource, public:
 
 WebDragSource::WebDragSource(gfx::NativeWindow source_wnd,
                              RenderViewHost* render_view_host)
     : BaseDragSource(),
       source_wnd_(source_wnd),
       render_view_host_(render_view_host) {
+  // In an effort to try to track down http://crbug.com/12524 we now CHECK
+  // when a NULL render_view_host is passed to us. I think this is what is
+  // happening but it is hard to tell since the minidump is not helpful in this
+  // case. At least we can then rule that out.
+  CHECK(render_view_host_);
 }
 
 void WebDragSource::OnDragSourceDrop() {
   gfx::Point client;
   gfx::Point screen;
   GetCursorPositions(source_wnd_, &client, &screen);
   render_view_host_->DragSourceEndedAt(client.x(), client.y(),
                                        screen.x(), screen.y());
 }
 
 void WebDragSource::OnDragSourceMove() {
   gfx::Point client;
   gfx::Point screen;
   GetCursorPositions(source_wnd_, &client, &screen);
   render_view_host_->DragSourceMovedTo(client.x(), client.y(),
                                        screen.x(), screen.y());
 }