ui/compositor: move the browser compositor thread to the ContextFactory

ui/aura/env.cc

Index: ui/aura/env.cc
diff --git a/ui/aura/env.cc b/ui/aura/env.cc
index bd074f91452da1d072b17bebc56a089e4140d65e..c10dc80daf4e55f75efb4c04799d469274b7ac2b 100644
--- a/ui/aura/env.cc
+++ b/ui/aura/env.cc
@@ -26,8 +26,6 @@ Env::Env()
 
 Env::~Env() {
   FOR_EACH_OBSERVER(EnvObserver, observers_, OnWillDestroyEnv());
-
-  ui::Compositor::Terminate();
 }
 
 //static
@@ -68,8 +66,6 @@ bool Env::IsMouseButtonDown() const {
 // Env, private:
 
 void Env::Init(bool create_event_source) {
-  ui::Compositor::Initialize();
-
   if (create_event_source && !ui::PlatformEventSource::GetInstance())
     event_source_ = ui::PlatformEventSource::CreateDefault();
 }