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

ui/wm/test/wm_test_helper.cc

Index: ui/wm/test/wm_test_helper.cc
diff --git a/ui/wm/test/wm_test_helper.cc b/ui/wm/test/wm_test_helper.cc
index dddb7af1c7d87471de2d10605cf0bd933cf555be..160923c8f36bcf4298d8d12c7e97da2ca4c0410f 100644
--- a/ui/wm/test/wm_test_helper.cc
+++ b/ui/wm/test/wm_test_helper.cc
@@ -9,7 +9,6 @@
 #include "ui/aura/env.h"
 #include "ui/aura/test/test_focus_client.h"
 #include "ui/aura/window.h"
-#include "ui/events/platform/platform_event_source.h"
 #include "ui/wm/core/compound_event_filter.h"
 #include "ui/wm/core/input_method_event_filter.h"
 
@@ -17,7 +16,6 @@ namespace wm {
 
 WMTestHelper::WMTestHelper(const gfx::Size& default_window_size) {
   aura::Env::CreateInstance();
-  event_source_ = ui::PlatformEventSource::CreateDefault();
   host_.reset(aura::WindowTreeHost::Create(gfx::Rect(default_window_size)));
   host_->InitHost();
   aura::client::SetWindowTreeClient(host_->window(), this);