Work in progress: Adds MessagePumpDispatcher::ShouldExit(). This is used to handle the

ash/accelerators/accelerator_dispatcher.cc

Index: ash/accelerators/accelerator_dispatcher.cc
diff --git a/ash/accelerators/accelerator_dispatcher.cc b/ash/accelerators/accelerator_dispatcher.cc
index e8c7fb2235adbaac2c96b36bb0d9e40ca1d00ceb..a7cc57d8cbe7c7259f2d872ab074903c43471159 100644
--- a/ash/accelerators/accelerator_dispatcher.cc
+++ b/ash/accelerators/accelerator_dispatcher.cc
@@ -90,4 +90,8 @@ bool AcceleratorDispatcher::Dispatch(const base::NativeEvent& event) {
   return nested_dispatcher_->Dispatch(event);
 }
 
+bool AcceleratorDispatcher::ShouldExit() {
+  return nested_dispatcher_->ShouldExit();
+}
+
 }  // namespace ash