Fixed issue where middle click doesn't activiate when not over its tab....

chrome/browser/views/tabs/tab.cc

Index: chrome/browser/views/tabs/tab.cc
===================================================================
--- chrome/browser/views/tabs/tab.cc	(revision 5817)
+++ chrome/browser/views/tabs/tab.cc	(working copy)
@@ -156,7 +156,11 @@
   // Notify the drag helper that we're done with any potential drag operations.
   // Clean up the drag helper, which is re-created on the next mouse press.
   delegate_->EndDrag(canceled);
-  if (event.IsMiddleMouseButton())
+
+  // Close tabs on middle click, but only if the button is released over the tab 
+  // (normal windows behavior is to discard presses of a UI element where the 
+  // releases happen off the element).
+  if (event.IsMiddleMouseButton() && HitTest(event.location()))
     delegate_->CloseTab(this);
 }