Prevent system modal dialog from blocking events to the virtual keyboard.

ash/root_window_controller.h

Index: ash/root_window_controller.h
diff --git a/ash/root_window_controller.h b/ash/root_window_controller.h
index ddf63555eec1d9a0f134320389c39d83acad223e..abb8b1f51b878829bb6d2246c797880f537819bb 100644
--- a/ash/root_window_controller.h
+++ b/ash/root_window_controller.h
@@ -234,6 +234,9 @@ class ASH_EXPORT RootWindowController : public ShellObserver {
   // Deactivate virtual keyboard on current root window controller.
   void DeactivateKeyboard(keyboard::KeyboardController* keyboard_controller);
 
+  // Tests if a window is associated with the virtual keyboard.
+  bool IsVirtualKeyboardWindow(aura::Window* window);
+
  private:
   explicit RootWindowController(aura::WindowTreeHost* host);
   enum RootWindowType {