Makes PlatformEventSource creation in Env conditional

ui/aura/env.cc

Index: ui/aura/env.cc
diff --git a/ui/aura/env.cc b/ui/aura/env.cc
index f701695738958abcfa6dd6e4753e31cf068fc7be..bd074f91452da1d072b17bebc56a089e4140d65e 100644
--- a/ui/aura/env.cc
+++ b/ui/aura/env.cc
@@ -31,10 +31,10 @@ Env::~Env() {
 }
 
 //static
-void Env::CreateInstance() {
+void Env::CreateInstance(bool create_event_source) {
   if (!instance_) {
     instance_ = new Env;
-    instance_->Init();
+    instance_->Init(create_event_source);
   }
 }
 
@@ -67,10 +67,10 @@ bool Env::IsMouseButtonDown() const {
 ////////////////////////////////////////////////////////////////////////////////
 // Env, private:
 
-void Env::Init() {
+void Env::Init(bool create_event_source) {
   ui::Compositor::Initialize();
 
-  if (!ui::PlatformEventSource::GetInstance())
+  if (create_event_source && !ui::PlatformEventSource::GetInstance())
     event_source_ = ui::PlatformEventSource::CreateDefault();
 }