Make ozone/drm/mojo more immune to startup races

ui/ozone/platform/drm/host/drm_cursor.cc

 // Copyright 2015 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/platform/drm/host/drm_cursor.h"
 
 #include "base/trace_event/trace_event.h"
 #include "ui/gfx/geometry/point_conversions.h"
 #include "ui/ozone/platform/drm/host/drm_window_host.h"
 #include "ui/ozone/platform/drm/host/drm_window_host_manager.h"
 
 #if defined(OS_CHROMEOS)
 #include "ui/events/ozone/chromeos/cursor_controller.h"
 #endif
 
 namespace ui {
 
 namespace {
 
 class NullProxy : public DrmCursorProxy {
  public:
   NullProxy() {}
   ~NullProxy() override {}
 
   void CursorSet(gfx::AcceleratedWidget window,
                  const std::vector<SkBitmap>& bitmaps,
                  const gfx::Point& point,
                  int frame_delay_ms) override {}
   void Move(gfx::AcceleratedWidget window, const gfx::Point& point) override {}
-  void InitializeOnEvdev() override {}
+  void InitializeOnEvdevIfNecessary() override {}
+  void SendToDelegate(DrmCursorProxy* delegate) override {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(NullProxy);
 };
 
 }  // namespace
 
 DrmCursor::DrmCursor(DrmWindowHostManager* window_manager)
     : window_(gfx::kNullAcceleratedWidget),
       window_manager_(window_manager),
       proxy_(new NullProxy()) {
   evdev_thread_checker_.DetachFromThread();
 }
 
 DrmCursor::~DrmCursor() {}
 
-void DrmCursor::SetDrmCursorProxy(DrmCursorProxy* proxy) {
+std::unique_ptr<DrmCursorProxy> DrmCursor::SetDrmCursorProxy(
+    std::unique_ptr<DrmCursorProxy> proxy) {
   TRACE_EVENT0("drmcursor", "DrmCursor::SetDrmCursorProxy");
   DCHECK(thread_checker_.CalledOnValidThread());
   base::AutoLock lock(lock_);
-  proxy_.reset(proxy);
+  std::swap(proxy, proxy_);
+  return proxy;
 }
 
 void DrmCursor::ResetDrmCursorProxy() {
   TRACE_EVENT0("drmcursor", "DrmCursor::ResetDrmCursorProxy");
   DCHECK(thread_checker_.CalledOnValidThread());
 
   NullProxy* np = new NullProxy();
   base::AutoLock lock(lock_);
   proxy_.reset(np);
 }
@@ skipping 147 matching lines @@
   return location_ + display_bounds_in_screen_.OffsetFromOrigin();
 }
 
 gfx::Rect DrmCursor::GetCursorConfinedBounds() {
   base::AutoLock lock(lock_);
   return confined_bounds_ + display_bounds_in_screen_.OffsetFromOrigin();
 }
 
 void DrmCursor::InitializeOnEvdev() {
   DCHECK(evdev_thread_checker_.CalledOnValidThread());
-  proxy_->InitializeOnEvdev();
+  proxy_->InitializeOnEvdevIfNecessary();
 }
 
 void DrmCursor::SetCursorLocationLocked(const gfx::PointF& location) {
   gfx::PointF clamped_location = location;
   clamped_location.SetToMax(gfx::PointF(confined_bounds_.origin()));
   // Right and bottom edges are exclusive.
   clamped_location.SetToMin(
       gfx::PointF(confined_bounds_.right() - 1, confined_bounds_.bottom() - 1));
 
   location_ = clamped_location;
@@ skipping 28 matching lines @@
 }
 
 void DrmCursor::MoveLockTested(gfx::AcceleratedWidget window,
                                const gfx::Point& point) {
   lock_.AssertAcquired();
   proxy_->Move(window, point);
 }
 
 
 }  // namespace ui