MacViews: Add WidgetEventGenerator to abstract platform-specific event generation for tests.

ash/test/ash_test_base.cc

Index: ash/test/ash_test_base.cc
diff --git a/ash/test/ash_test_base.cc b/ash/test/ash_test_base.cc
index cfd3142848f277ff8834ebaeb1e90082ec46ee30..aae88443a3f16a07b7ccdeb74a4b29b698c18728 100644
--- a/ash/test/ash_test_base.cc
+++ b/ash/test/ash_test_base.cc
@@ -55,12 +55,13 @@ namespace ash {
 namespace test {
 namespace {
 
-class AshEventGeneratorDelegate : public aura::test::EventGeneratorDelegate {
+class AshEventGeneratorDelegate
+    : public aura::test::EventGeneratorDelegateAura {
  public:
   AshEventGeneratorDelegate() {}
   virtual ~AshEventGeneratorDelegate() {}
 
-  // aura::test::EventGeneratorDelegate overrides:
+  // aura::test::EventGeneratorDelegateAura overrides:
   virtual aura::WindowTreeHost* GetHostAt(
       const gfx::Point& point_in_screen) const OVERRIDE {
     gfx::Screen* screen = Shell::GetScreen();