Prevent browser crash resulting from misbehaving WebVR renderer requesting multiple VSyncs.

chrome/browser/android/vr_shell/non_presenting_gvr_delegate.cc

 // 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 "chrome/browser/android/vr_shell/non_presenting_gvr_delegate.h"
 
 #include <utility>
 
 #include "base/callback_helpers.h"
 #include "chrome/browser/android/vr_shell/vr_shell.h"
@@ skipping 43 matching lines @@
 NonPresentingGvrDelegate::OnSwitchToPresentingDelegate() {
   StopVSyncLoop();
   if (binding_.is_bound())
     return binding_.Unbind();
   return nullptr;
 }
 
 void NonPresentingGvrDelegate::StopVSyncLoop() {
   vsync_task_.Cancel();
   if (!callback_.is_null()) {
-    base::ResetAndReturn(&callback_).Run(nullptr, base::TimeDelta(), -1);
+    base::ResetAndReturn(&callback_)
+        .Run(nullptr, base::TimeDelta(), -1,
+             device::mojom::VRVSyncProvider::Error::ERROR_TRY_AGAIN);
   }
   gvr_api_->PauseTracking();
   // If the loop is stopped, it's not considered to be paused.
   vsync_paused_ = false;
 }
 
 void NonPresentingGvrDelegate::StartVSyncLoop() {
   vsync_task_.Reset(
       base::Bind(&NonPresentingGvrDelegate::OnVSync, base::Unretained(this)));
   gvr_api_->RefreshViewerProfile();
@@ skipping 28 matching lines @@
     pending_vsync_ = true;
     pending_time_ = time;
   }
 }
 
 void NonPresentingGvrDelegate::GetVSync(const GetVSyncCallback& callback) {
   if (!pending_vsync_) {
     if (!callback_.is_null()) {
       mojo::ReportBadMessage("Requested VSync before waiting for response to "
           "previous request.");
+      callback.Run(nullptr, base::TimeDelta(), -1,
+                   device::mojom::VRVSyncProvider::Error::ERROR_BAD_REQUEST);
       return;
     }
     callback_ = callback;
     return;
   }
   pending_vsync_ = false;
   SendVSync(pending_time_, callback);
 }
 
 void NonPresentingGvrDelegate::UpdateVSyncInterval(int64_t timebase_nanos,
                                                    double interval_seconds) {
   vsync_timebase_ = base::TimeTicks();
   vsync_timebase_ += base::TimeDelta::FromMicroseconds(timebase_nanos / 1000);
   vsync_interval_ = base::TimeDelta::FromSecondsD(interval_seconds);
   StartVSyncLoop();
 }
 
 void NonPresentingGvrDelegate::SendVSync(base::TimeDelta time,
                                          const GetVSyncCallback& callback) {
   gvr::ClockTimePoint target_time = gvr::GvrApi::GetTimePointNow();
   target_time.monotonic_system_time_nanos += kPredictionTimeWithoutVsyncNanos;
 
   gvr::Mat4f head_mat = gvr_api_->ApplyNeckModel(
       gvr_api_->GetHeadSpaceFromStartSpaceRotation(target_time), 1.0f);
-  callback.Run(VrShell::VRPosePtrFromGvrPose(head_mat), time, -1);
+  callback.Run(VrShell::VRPosePtrFromGvrPose(head_mat), time, -1,
+               device::mojom::VRVSyncProvider::Error::ERROR_NONE);
 }
 
 bool NonPresentingGvrDelegate::SupportsPresentation() {
   return false;
 }
 
 void NonPresentingGvrDelegate::ResetPose() {
   // Should never call RecenterTracking when using with Daydream viewers. On
   // those devices recentering should only be done via the controller.
   if (gvr_api_ && gvr_api_->GetViewerType() == GVR_VIEWER_TYPE_CARDBOARD)
     gvr_api_->RecenterTracking();
 }
 
 void NonPresentingGvrDelegate::CreateVRDisplayInfo(
     const base::Callback<void(device::mojom::VRDisplayInfoPtr)>& callback,
     uint32_t device_id) {
   callback.Run(VrShell::CreateVRDisplayInfo(
       gvr_api_.get(), device::kInvalidRenderTargetSize, device_id));
 }
 
 }  // namespace vr_shell