Removing an unneeded Untraced from vr_display

Untraced should be avoided where possible.

Bug: 874627
Cq-Include-Trybots: luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: I1e9c4ed7e800362f3a4b9a7ecd5aaf148ddd8a9a
Reviewed-on: https://chromium-review.googlesource.com/1180166Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Anna Offenwanger <offenwanger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#584482}

third_party/blink/renderer/modules/vr/vr_display.cc

@@ -120,6 +120,9 @@ void SessionClientBinding::OnBlur() {
 void SessionClientBinding::OnFocus() {
   display_->OnFocus(is_immersive_);
 };
+void SessionClientBinding::Trace(blink::Visitor* visitor) {
+  visitor->Trace(display_);
+}
 
 VRDisplay::VRDisplay(NavigatorVR* navigator_vr,
                      device::mojom::blink::XRDevicePtr device)
@@ -560,7 +563,7 @@ void VRDisplay::OnRequestImmersiveSessionReturned(
 
     if (immersive_client_binding_)
       immersive_client_binding_->Close();
-    immersive_client_binding_ = std::make_unique<SessionClientBinding>(
+    immersive_client_binding_ = new SessionClientBinding(
         this, false, std::move(session->client_request));
 
     Update(std::move(session->display_info));
@@ -585,8 +588,8 @@ void VRDisplay::OnNonImmersiveSessionRequestReturned(
     return;
   }
   non_immersive_provider_.Bind(std::move(session->data_provider));
-  non_immersive_client_binding_ = std::make_unique<SessionClientBinding>(
-      this, false, std::move(session->client_request));
+  non_immersive_client_binding_ =
+      new SessionClientBinding(this, false, std::move(session->client_request));
   RequestVSync();
 }
 
@@ -1184,6 +1187,8 @@ void VRDisplay::Trace(blink::Visitor* visitor) {
   visitor->Trace(rendering_context_);
   visitor->Trace(frame_transport_);
   visitor->Trace(scripted_animation_controller_);
+  visitor->Trace(non_immersive_client_binding_);
+  visitor->Trace(immersive_client_binding_);
   visitor->Trace(pending_present_resolvers_);
   EventTargetWithInlineData::Trace(visitor);
   ContextLifecycleObserver::Trace(visitor);

third_party/blink/renderer/modules/vr/vr_display.h

@@ -41,7 +41,9 @@ class WebGLRenderingContextBase;
 
 // Wrapper class to allow the VRDisplay to distinguish between immersive and
 // non-immersive XRSession events.
-class SessionClientBinding : public device::mojom::blink::XRSessionClient {
+class SessionClientBinding
+    : public GarbageCollectedFinalized<SessionClientBinding>,
+      public device::mojom::blink::XRSessionClient {
  public:
   SessionClientBinding(VRDisplay* display,
                        bool is_immersive,
@@ -49,6 +51,8 @@ class SessionClientBinding : public device::mojom::blink::XRSessionClient {
   ~SessionClientBinding() override;
   void Close();
 
+  void Trace(blink::Visitor*);
+
  private:
   void OnChanged(device::mojom::blink::VRDisplayInfoPtr) override;
   void OnExitPresent() override;
@@ -57,7 +61,7 @@ class SessionClientBinding : public device::mojom::blink::XRSessionClient {
 
   // VRDisplay keeps all references to SessionClientBinding, so as soon as
   // VRDisplay is destroyed, so is the SessionClientBinding.
-  UntracedMember<VRDisplay> display_;
+  Member<VRDisplay> display_;
   bool is_immersive_;
   mojo::Binding<device::mojom::blink::XRSessionClient> client_binding_;
 };
@@ -250,8 +254,8 @@ class VRDisplay final : public EventTargetWithInlineData,
 
   bool present_image_needs_copy_ = false;
 
-  std::unique_ptr<SessionClientBinding> non_immersive_client_binding_;
-  std::unique_ptr<SessionClientBinding> immersive_client_binding_;
+  Member<SessionClientBinding> non_immersive_client_binding_;
+  Member<SessionClientBinding> immersive_client_binding_;
   mojo::Binding<device::mojom::blink::VRDisplayClient> display_client_binding_;
   device::mojom::blink::XRFrameDataProviderPtr vr_presentation_data_provider_;
   device::mojom::blink::XRPresentationProviderPtr vr_presentation_provider_;