events: Move the PlatformEventSource creation in aura::Env.

ui/wm/test/wm_test_helper.h

Index: ui/wm/test/wm_test_helper.h
diff --git a/ui/wm/test/wm_test_helper.h b/ui/wm/test/wm_test_helper.h
index 1bde9f33f7a3388c93f344a581ab50a9309cb34f..6d2a265944878c69510f913a941d10a1e269ff18 100644
--- a/ui/wm/test/wm_test_helper.h
+++ b/ui/wm/test/wm_test_helper.h
@@ -25,10 +25,6 @@ class Rect;
 class Size;
 }
 
-namespace ui {
-class PlatformEventSource;
-}
-
 namespace wm {
 
 class CompoundEventFilter;
@@ -59,7 +55,6 @@ class WMTestHelper : public aura::client::WindowTreeClient {
   scoped_ptr<wm::InputMethodEventFilter> input_method_filter_;
   scoped_ptr<aura::client::DefaultActivationClient> activation_client_;
   scoped_ptr<aura::client::FocusClient> focus_client_;
-  scoped_ptr<ui::PlatformEventSource> event_source_;
 
   DISALLOW_COPY_AND_ASSIGN(WMTestHelper);
 };