Fix a GPU watchdog V2 DCHECK in GPU initialization

A DCHECK is triggered in GpuWatchdogThreadImplV2::Arm() during GPU
initialization. Whenever there is an error, GpuInit::InitializeAndStartSandbox()
exits earlier. watchdog_thread_->OnInitComplete() is not called in those cases
and arm_disarm_counter_ gets messed up.
A new class GpuWatchdogInit is created to call OnInitcomplete() in the destructor.
OnInitComplete() will never be missed at the end of InitializeAndStartSandbox().

Bug:949839, 995372

Change-Id: I1a107df0ca48409ff2252260ea41de643fa39b6c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1762879Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Commit-Queue: Maggie Chen <magchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#689343}

gpu/ipc/service/gpu_init.cc

@@ -122,6 +122,20 @@ bool CanAccessNvidiaDeviceFile() {
 }
 #endif  // OS_LINUX && !OS_CHROMEOS && !IS_CHROMECAST
 
+class GpuWatchdogInit {
+ public:
+  GpuWatchdogInit() = default;
+  ~GpuWatchdogInit() {
+    if (watchdog_ptr_)
+      watchdog_ptr_->OnInitComplete();
+  }
+
+  void SetGpuWatchdogPtr(gpu::GpuWatchdogThread* ptr) { watchdog_ptr_ = ptr; }
+
+ private:
+  gpu::GpuWatchdogThread* watchdog_ptr_ = nullptr;
+};
+
 }  // namespace
 
 GpuInit::GpuInit() = default;
@@ -191,6 +205,10 @@ bool GpuInit::InitializeAndStartSandbox(base::CommandLine* command_line,
   enable_watchdog = false;
 #endif
 
+  // watchdog_init will call watchdog OnInitComplete() at the end of this
+  // function.
+  GpuWatchdogInit watchdog_init;
+
   bool delayed_watchdog_enable = false;
 
 #if defined(OS_CHROMEOS)
@@ -205,6 +223,7 @@ bool GpuInit::InitializeAndStartSandbox(base::CommandLine* command_line,
     if (base::FeatureList::IsEnabled(features::kGpuWatchdogV2)) {
       watchdog_thread_ = gpu::GpuWatchdogThreadImplV2::Create(
           gpu_preferences_.watchdog_starts_backgrounded);
+      watchdog_init.SetGpuWatchdogPtr(watchdog_thread_.get());
     } else {
       watchdog_thread_ = gpu::GpuWatchdogThreadImplV1::Create(
           gpu_preferences_.watchdog_starts_backgrounded);
@@ -415,6 +434,7 @@ bool GpuInit::InitializeAndStartSandbox(base::CommandLine* command_line,
     if (base::FeatureList::IsEnabled(features::kGpuWatchdogV2)) {
       watchdog_thread_ = gpu::GpuWatchdogThreadImplV2::Create(
           gpu_preferences_.watchdog_starts_backgrounded);
+      watchdog_init.SetGpuWatchdogPtr(watchdog_thread_.get());
     } else {
       watchdog_thread_ = gpu::GpuWatchdogThreadImplV1::Create(
           gpu_preferences_.watchdog_starts_backgrounded);
@@ -430,11 +450,6 @@ bool GpuInit::InitializeAndStartSandbox(base::CommandLine* command_line,
   UMA_HISTOGRAM_BOOLEAN("GPU.Sandbox.InitializedSuccessfully",
                         gpu_info_.sandboxed);
 
-  // Notify the gpu watchdog that the gpu init has completed So the watchdog
-  // can be disarmed.
-  if (watchdog_thread_)
-    watchdog_thread_->OnInitComplete();
-
   init_successful_ = true;
 #if defined(USE_OZONE)
   ui::OzonePlatform::GetInstance()->AfterSandboxEntry();