Fixing browser crash in the linux tab dragging code.

chrome/browser/ui/gtk/tabs/dragged_tab_controller_gtk.cc

Index: chrome/browser/ui/gtk/tabs/dragged_tab_controller_gtk.cc
diff --git a/chrome/browser/ui/gtk/tabs/dragged_tab_controller_gtk.cc b/chrome/browser/ui/gtk/tabs/dragged_tab_controller_gtk.cc
index 5a87dc290c45c375c17481be0aff8cc73893d52e..edb4acc7913b0a0edbfba80e775d68a7dc9dcd55 100644
--- a/chrome/browser/ui/gtk/tabs/dragged_tab_controller_gtk.cc
+++ b/chrome/browser/ui/gtk/tabs/dragged_tab_controller_gtk.cc
@@ -86,7 +86,8 @@ void DraggedTabControllerGtk::CaptureDragInfo(const gfx::Point& mouse_offset) {
 
 void DraggedTabControllerGtk::Drag() {
   if (!drag_data_->GetSourceTabData()->tab_ ||
-      !drag_data_->GetSourceTabContentsWrapper()) {
+      !drag_data_->GetSourceTabContentsWrapper() ||
+      !drag_data_->GetSourceTabContents()) {
     return;
   }