Fix a renderer crash when dragging quickly over tab contents.

content/browser/web_contents/web_drag_dest_gtk.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_drag_dest_gtk.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/file_path.h"
@@ skipping 73 matching lines @@
 void WebDragDestGtk::UpdateDragStatus(WebDragOperation operation) {
   if (context_) {
     is_drop_target_ = operation != WebDragOperationNone;
     gdk_drag_status(context_, content::WebDragOpToGdkDragAction(operation),
                     drag_over_time_);
   }
 }
 
 void WebDragDestGtk::DragLeave() {
   GetRenderViewHost()->DragTargetDragLeave();
-
   if (delegate())
     delegate()->OnDragLeave();
 
   drop_data_.reset();
 }
 
 gboolean WebDragDestGtk::OnDragMotion(GtkWidget* sender,
                                       GdkDragContext* context,
                                       gint x, gint y,
                                       guint time) {
@@ skipping 158 matching lines @@
   }
 }
 
 // The drag has left our widget; forward this information to the renderer.
 void WebDragDestGtk::OnDragLeave(GtkWidget* sender, GdkDragContext* context,
                                  guint time) {
   // Set |context_| to NULL to make sure we will recognize the next DragMotion
   // as an enter.
   context_ = NULL;
 
+  // Sometimes we get a drag-leave event before getting a drag-data-received
+  // event. In that case, we don't want to bother the renderer with a
+  // DragLeave event.
+  if (data_requests_ != 0)
+    return;
+
   // When GTK sends us a drag-drop signal, it is shortly (and synchronously)
   // preceded by a drag-leave. The renderer doesn't like getting the signals
   // in this order so delay telling it about the drag-leave till we are sure
   // we are not getting a drop as well.
   MessageLoop::current()->PostTask(FROM_HERE,
       base::Bind(&WebDragDestGtk::DragLeave, method_factory_.GetWeakPtr()));
 }
 
 // Called by GTK when the user releases the mouse, executing a drop.
 gboolean WebDragDestGtk::OnDragDrop(GtkWidget* sender, GdkDragContext* context,
@@ skipping 14 matching lines @@
   gtk_drag_finish(context, is_drop_target_, FALSE, time);
 
   return TRUE;
 }
 
 RenderViewHostImpl* WebDragDestGtk::GetRenderViewHost() const {
   return static_cast<RenderViewHostImpl*>(web_contents_->GetRenderViewHost());
 }
 
 }  // namespace content