Ozone/DRM: Fix cursor remote being rebound on every cursor move

This CL fixes two issues:
- |evdev_bound_| is never set, so we keep rebinding |evdev_cursor_| on
  every cursor move.
- |evdev_cursor_| was initially bound on the UI thread so calling
  Unbind() on the evdev thread for the first time triggers a DCHECK.
  Instead keep the pending remote unbound until it's time to bind it on
  the evdev thread.

Bug: 620927,1039834
Change-Id: Iea19d5e32b0cbc9396f7b5e178e8e4ab6001f8c4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1997646
Commit-Queue: Saman Sami <samans@chromium.org>
Reviewed-by: Michael Spang <spang@chromium.org>
Auto-Submit: Saman Sami <samans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#731618}

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

@@ -16,7 +16,7 @@ HostCursorProxy::HostCursorProxy(
     mojo::PendingAssociatedRemote<ui::ozone::mojom::DeviceCursor> main_cursor,
     mojo::PendingAssociatedRemote<ui::ozone::mojom::DeviceCursor> evdev_cursor)
     : main_cursor_(std::move(main_cursor)),
-      evdev_cursor_(std::move(evdev_cursor)),
+      evdev_cursor_pending_remote_(std::move(evdev_cursor)),
       ui_thread_ref_(base::PlatformThread::CurrentRef()) {}
 
 HostCursorProxy::~HostCursorProxy() {}
@@ -25,39 +25,28 @@ void HostCursorProxy::CursorSet(gfx::AcceleratedWidget widget,
                                 const std::vector<SkBitmap>& bitmaps,
                                 const gfx::Point& location,
                                 int frame_delay_ms) {
-  InitializeOnEvdevIfNecessary();
   if (ui_thread_ref_ == base::PlatformThread::CurrentRef()) {
     main_cursor_->SetCursor(widget, bitmaps, location, frame_delay_ms);
   } else {
+    InitializeOnEvdevIfNecessary();
     evdev_cursor_->SetCursor(widget, bitmaps, location, frame_delay_ms);
   }
 }
 
 void HostCursorProxy::Move(gfx::AcceleratedWidget widget,
                            const gfx::Point& location) {
-  InitializeOnEvdevIfNecessary();
   if (ui_thread_ref_ == base::PlatformThread::CurrentRef()) {
     main_cursor_->MoveCursor(widget, location);
   } else {
+    InitializeOnEvdevIfNecessary();
     evdev_cursor_->MoveCursor(widget, location);
   }
 }
 
-// Evdev runs this method on starting. But if a HostCursorProxy is created long
-// after Evdev has started (e.g. if the Viz process crashes (and the
-// |HostCursorProxy| self-destructs and then a new |HostCursorProxy| is built
-// when the GpuThread/DrmThread pair are once again running), we need to run it
-// on cursor motions.
 void HostCursorProxy::InitializeOnEvdevIfNecessary() {
-  // TODO(rjkroege): Rebind on Viz process restart.
-  if (evdev_bound_)
+  if (evdev_cursor_.is_bound())
     return;
-
-  if (ui_thread_ref_ != base::PlatformThread::CurrentRef()) {
-    // Rebind the mojo pipe on the current thread. We expect this to be the
-    // thread running EVDEV.
-    evdev_cursor_.Bind(evdev_cursor_.Unbind());
-  }
+  evdev_cursor_.Bind(std::move(evdev_cursor_pending_remote_));
 }
 
 }  // namespace ui

ui/ozone/platform/drm/host/host_cursor_proxy.h

@@ -35,12 +35,15 @@ class HostCursorProxy : public DrmCursorProxy {
   void Move(gfx::AcceleratedWidget window, const gfx::Point& point) override;
   void InitializeOnEvdevIfNecessary() override;
 
-  // Mojo implementation of the DrmCursorProxy.
+  // Accessed from UI thread only.
   mojo::AssociatedRemote<ui::ozone::mojom::DeviceCursor> main_cursor_;
+
+  // Accessed from evdev thread only.
   mojo::AssociatedRemote<ui::ozone::mojom::DeviceCursor> evdev_cursor_;
+  mojo::PendingAssociatedRemote<ui::ozone::mojom::DeviceCursor>
+      evdev_cursor_pending_remote_;
 
   base::PlatformThreadRef ui_thread_ref_;
-  bool evdev_bound_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(HostCursorProxy);
 };