Use a mocked compositor for unit tests

views/widget/widget.h

Index: views/widget/widget.h
diff --git a/views/widget/widget.h b/views/widget/widget.h
index 17413c3db9e6d91fb554bac871c2d7fd8eb86289..caaf29860e7f7d49b62d9999bcb0ebcf728ad806 100644
--- a/views/widget/widget.h
+++ b/views/widget/widget.h
@@ -43,6 +43,7 @@ class Rect;
 namespace ui {
 class Accelerator;
 class Compositor;
+class CompositorDelegate;
 class OSExchangeData;
 class ThemeProvider;
 enum TouchStatus;
@@ -496,10 +497,12 @@ class VIEWS_EXPORT Widget : public internal::NativeWidgetDelegate,
     return non_client_view_ ? non_client_view_->client_view() : NULL;
   }
 
-  static void set_compositor_factory_for_testing(ui::Compositor*(*factory)()) {
+  static void set_compositor_factory_for_testing(
+      ui::Compositor*(*factory)(ui::CompositorDelegate* owner)) {
     compositor_factory_ = factory;
   }
-  static ui::Compositor* (*compositor_factory())() {
+  static ui::Compositor* (*compositor_factory())(
+      ui::CompositorDelegate* owner) {
     return compositor_factory_;
   }
 
@@ -723,7 +726,10 @@ class VIEWS_EXPORT Widget : public internal::NativeWidgetDelegate,
   bool is_top_level_;
 
   // Factory used to create Compositors. Settable by tests.
-  static ui::Compositor*(*compositor_factory_)();
+  // The delegate can be NULL if you don't wish to catch the ScheduleDraw()
+  // calls to it.
+  static ui::Compositor*(*compositor_factory_)(
+      ui::CompositorDelegate* delegate);
 
   // Tracks whether native widget has been initialized.
   bool native_widget_initialized_;