Bug 100180 - Modal dialogs should try to cancel any drag sessions in progress. r=roc.

dom/base/nsGlobalWindow.cpp

@@ -8430,6 +8430,13 @@ nsGlobalWindow::EnterModalState()
     }
   }
 
+  // If there are any drag and drop operations in flight, try to end them.
+  nsCOMPtr<nsIDragService> ds =
+    do_GetService("@mozilla.org/widget/dragservice;1");
+  if (ds) {
+    ds->EndDragSession(true);
+  }
+
   // Clear the capturing content if it is under topDoc.
   // Usually the activeESM check above does that, but there are cases when
   // we don't have activeESM, or it is for different document.

widget/windows/nsDragService.cpp

@@ -591,6 +591,13 @@ nsDragService::IsCollectionObject(IDataObject* inDataObj)
 NS_IMETHODIMP
 nsDragService::EndDragSession(bool aDoneDrag)
 {
+  // Bug 100180: If we've got mouse events captured, make sure we release it -
+  // that way, if we happen to call EndDragSession before diving into a nested
+  // event loop, we can still respond to mouse events.
+  if (::GetCapture()) {
+    ::ReleaseCapture();
+  }
+
   nsBaseDragService::EndDragSession(aDoneDrag);
   NS_IF_RELEASE(mDataObject);