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

ash/root_window_controller.cc

Index: ash/root_window_controller.cc
diff --git a/ash/root_window_controller.cc b/ash/root_window_controller.cc
index 3b1fbce32464198103344831a8c90055172747f7..93fb912ab537dc206c6b4124e0372ab9a7b4e68c 100644
--- a/ash/root_window_controller.cc
+++ b/ash/root_window_controller.cc
@@ -652,6 +652,12 @@ void RootWindowController::DeactivateKeyboard(
   }
 }
 
+bool RootWindowController::IsVirtualKeyboardWindow(aura::Window* window) {
+  aura::Window* parent = GetContainer(
+      kShellWindowId_VirtualKeyboardParentContainer);
+  return parent ? parent->Contains(window) : false;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // RootWindowController, private: