Linux Sandbox: Stop GPU watchdog in accountable way.

content/gpu/gpu_main.cc

Index: content/gpu/gpu_main.cc
diff --git a/content/gpu/gpu_main.cc b/content/gpu/gpu_main.cc
index 713b3373b63f32e98adbf31379695ef6606c16fb..4086e96f6e3763bff4093323a9777e7695db77c0 100644
--- a/content/gpu/gpu_main.cc
+++ b/content/gpu/gpu_main.cc
@@ -422,13 +422,17 @@ bool StartSandboxLinux(const gpu::GPUInfo& gpu_info,
 
   WarmUpSandboxNvidia(gpu_info, should_initialize_gl_context);
 
-  if (watchdog_thread)
-    watchdog_thread->Stop();
+  if (watchdog_thread) {
+    // LinuxSandbox needs to be able to ensure that the thread
+    // has really been stopped.
+    LinuxSandbox::StopThread(watchdog_thread);
+  }
   // LinuxSandbox::InitializeSandbox() must always be called
   // with only one thread.
   res = LinuxSandbox::InitializeSandbox();
-  if (watchdog_thread)
+  if (watchdog_thread) {
     watchdog_thread->Start();
+  }
 
   return res;
 }