WebVR: flush before requesting sync token for mailbox

third_party/WebKit/Source/modules/vr/VRDisplay.cpp

 // Copyright 2016 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 "modules/vr/VRDisplay.h"
 
 #include "core/css/StylePropertySet.h"
 #include "core/dom/DOMException.h"
 #include "core/dom/FrameRequestCallback.h"
 #include "core/dom/ScriptedAnimationController.h"
@@ skipping 593 matching lines @@
     while (pending_previous_frame_render_) {
       if (!submit_frame_client_binding_.WaitForIncomingMethodCall()) {
         DLOG(ERROR) << "Failed to receive SubmitFrame response";
         break;
       }
     }
   }
 
   pending_previous_frame_render_ = true;
   pending_submit_frame_ = true;
-  display_->SubmitFrame(
-      vr_frame_id_,
-      gpu::MailboxHolder(static_image->GetMailbox(),
-                         static_image->GetSyncToken(), GL_TEXTURE_2D));
+
+  TRACE_EVENT_BEGIN0("gpu", "VRDisplay::GetMailbox");
+  auto mailbox = static_image->GetMailbox();
+  TRACE_EVENT_END0("gpu", "VRDisplay::GetMailbox");
+  // Flush to avoid black screen flashes which appear to be related to
+  // "fence sync must be flushed before generating sync token" GL errors.
+  context_gl_->Flush();
+  TRACE_EVENT_BEGIN0("gpu", "VRDisplay::GetSyncToken");
+  auto token = static_image->GetSyncToken();

[mthiesse, 2017/05/18 15:33:53]

s/token/sync_token

[klausw, 2017/05/18 17:47:39]

Done, this was a cherry-pick with a bad manual edit.

+  TRACE_EVENT_END0("gpu", "VRDisplay::GetSyncToken");
+  TRACE_EVENT_BEGIN0("gpu", "VRDisplay::SubmitFrame");
+  display_->SubmitFrame(vr_frame_id_,
+                        gpu::MailboxHolder(mailbox, sync_token, GL_TEXTURE_2D));
   did_submit_this_frame_ = true;
   RequestVSync();
+  TRACE_EVENT_END0("gpu", "VRDisplay::SubmitFrame");
 
   // If preserveDrawingBuffer is false, must clear now. Normally this
   // happens as part of compositing, but that's not active while
   // presenting, so run the responsible code directly.
   rendering_context_->MarkCompositedAndClearBackbufferIfNeeded();
 
   // If we're not deferring the wait for transferring the mailbox,
   // we need to wait for it now to prevent the image going out of
   // scope before its mailbox is retrieved.
   if (!wait_for_previous_transfer_to_finish) {
@@ skipping 267 matching lines @@
   visitor->Trace(stage_parameters_);
   visitor->Trace(eye_parameters_left_);
   visitor->Trace(eye_parameters_right_);
   visitor->Trace(layer_);
   visitor->Trace(rendering_context_);
   visitor->Trace(scripted_animation_controller_);
   visitor->Trace(pending_present_resolvers_);
 }
 
 }  // namespace blink