Make middle-clicking on GTK tabs not count for closing if you release off of ...

chrome/browser/gtk/tabs/tab_gtk.cc

Index: chrome/browser/gtk/tabs/tab_gtk.cc
===================================================================
--- chrome/browser/gtk/tabs/tab_gtk.cc	(revision 21184)
+++ chrome/browser/gtk/tabs/tab_gtk.cc	(working copy)
@@ -175,7 +175,12 @@
 // static
 gboolean TabGtk::OnMouseRelease(GtkWidget* widget, GdkEventButton* event,
                                 TabGtk* tab) {
-  if (event->button == 2) {
+  // Middle mouse up means close the tab, but only if the mouse is over it
+  // (like a button).
+  if (event->button == 2 &&
+      event->x >= 0 && event->y >= 0 &&
+      event->x < widget->allocation.width &&
+      event->y < widget.allocation.height) {
     tab->delegate_->CloseTab(tab);
   }