WIP fix for Ozone cursor woes in Mushrome: Numéro deux

ui/ozone/public/cursor_factory_ozone.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/ozone/public/cursor_factory_ozone.h"
 
+#include "base/lazy_instance.h"
 #include "base/logging.h"
+#include "base/threading/thread_local.h"
 
 namespace ui {
+namespace {
 
-// static
-CursorFactoryOzone* CursorFactoryOzone::impl_ = NULL;
+base::LazyInstance<base::ThreadLocalPointer<CursorFactoryOzone>>::Leaky
+    lazy_tls_ptr = LAZY_INSTANCE_INITIALIZER;
+}
 
 CursorFactoryOzone::CursorFactoryOzone() {
-  DCHECK(!impl_) << "There should only be a single CursorFactoryOzone.";
-  impl_ = this;
+  DCHECK(!lazy_tls_ptr.Pointer()->Get())
+      << "There should only be a single CursorFactoryOzone per thread.";
+  lazy_tls_ptr.Pointer()->Set(this);
 }
 
 CursorFactoryOzone::~CursorFactoryOzone() {
-  DCHECK_EQ(impl_, this);
-  impl_ = NULL;
+  DCHECK_EQ(lazy_tls_ptr.Pointer()->Get(), this);
+  lazy_tls_ptr.Pointer()->Set(nullptr);
 }
 
 CursorFactoryOzone* CursorFactoryOzone::GetInstance() {
-  DCHECK(impl_) << "No CursorFactoryOzone implementation set.";
-  return impl_;
+  CursorFactoryOzone* result = lazy_tls_ptr.Pointer()->Get();
+  DCHECK(result) << "No CursorFactoryOzone implementation set.";
+  return result;
 }
 
 PlatformCursor CursorFactoryOzone::GetDefaultCursor(CursorType type) {
   NOTIMPLEMENTED();
   return NULL;
 }
 
 PlatformCursor CursorFactoryOzone::CreateImageCursor(const SkBitmap& bitmap,
                                                      const gfx::Point& hotspot,
                                                      float bitmap_dpi) {
@@ skipping 12 matching lines @@
 
 void CursorFactoryOzone::RefImageCursor(PlatformCursor cursor) {
   NOTIMPLEMENTED();
 }
 
 void CursorFactoryOzone::UnrefImageCursor(PlatformCursor cursor) {
   NOTIMPLEMENTED();
 }
 
 }  // namespace ui