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..8924746525c8a6676806bfa0f5c18523e85e613c 100644
--- a/ash/test/ash_test_base.cc
+++ b/ash/test/ash_test_base.cc
@@ -55,7 +55,8 @@ namespace ash {
 namespace test {
 namespace {
 
-class AshEventGeneratorDelegate : public aura::test::EventGeneratorDelegate {
+class AshEventGeneratorDelegate
+    : public aura::test::EventGeneratorDelegateAura {
  public:
   AshEventGeneratorDelegate() {}
   virtual ~AshEventGeneratorDelegate() {}