[Ozone-Dri] Decouple the IO helper thread from DriWrapper

ui/ozone/platform/dri/dri_gpu_platform_support.cc

Index: ui/ozone/platform/dri/dri_gpu_platform_support.cc
diff --git a/ui/ozone/platform/dri/dri_gpu_platform_support.cc b/ui/ozone/platform/dri/dri_gpu_platform_support.cc
index 13c16da2cd14a1af78f3f08dd8198ecd81ee7bd4..a9036b4a1f097aaff27e2fd0ed18707fc3654f1f 100644
--- a/ui/ozone/platform/dri/dri_gpu_platform_support.cc
+++ b/ui/ozone/platform/dri/dri_gpu_platform_support.cc
@@ -12,6 +12,7 @@
 #include "ui/ozone/common/display_util.h"
 #include "ui/ozone/common/gpu/ozone_gpu_message_params.h"
 #include "ui/ozone/common/gpu/ozone_gpu_messages.h"
+#include "ui/ozone/platform/dri/dri_helper_thread.h"
 #include "ui/ozone/platform/dri/dri_window_delegate_impl.h"
 #include "ui/ozone/platform/dri/dri_window_delegate_manager.h"
 #include "ui/ozone/platform/dri/native_display_delegate_dri.h"
@@ -29,8 +30,10 @@ void MessageProcessedOnMain(
 class DriGpuPlatformSupportMessageFilter : public IPC::MessageFilter {
  public:
   DriGpuPlatformSupportMessageFilter(DriWindowDelegateManager* window_manager,
+                                     DriHelperThread* helper_thread,
                                      IPC::Listener* main_thread_listener)
       : window_manager_(window_manager),
+        helper_thread_(helper_thread),
         main_thread_listener_(main_thread_listener),
         main_thread_task_runner_(base::ThreadTaskRunnerHandle::Get()),
         pending_main_thread_operations_(0),
@@ -39,6 +42,8 @@ class DriGpuPlatformSupportMessageFilter : public IPC::MessageFilter {
 
   void OnFilterAdded(IPC::Sender* sender) override {
     io_thread_task_runner_ = base::ThreadTaskRunnerHandle::Get();
+    if (helper_thread_)

[alexst (slow to review), 2015/01/22 23:09:24]

So it occurred to me, we shouldn't be passing the helper_thread object between
the threads, that's not safe, the only thing that should cross thread boundaries
is the task runner.

If we call init it here, the dri_wrapper could be getting the task runner while
it's being set on another thread. It's racy.

I am thinking, should we create the thread object and initialize it here and
pass its task_runner to dri by posting to main instead?

Eventually, we will need the task runner here in the filter as well because
that's where the messages will go.

[dnicoara, 2015/01/23 17:13:06]

Done.

I've moved the helper thread in here and Initialized on main as per your
suggestion.

I think we'll need to move the helper thread but currently it is not clear to me
how the GPU initialization needs to be ordered so I'm taking it one step at a
time.

+      helper_thread_->Initialize();
   }
 
   // This code is meant to be very temporary and only as a special case to fix
@@ -148,6 +153,7 @@ class DriGpuPlatformSupportMessageFilter : public IPC::MessageFilter {
   }
 
   DriWindowDelegateManager* window_manager_;
+  DriHelperThread* helper_thread_;
   IPC::Listener* main_thread_listener_;
   scoped_refptr<base::SingleThreadTaskRunner> main_thread_task_runner_;
   scoped_refptr<base::SingleThreadTaskRunner> io_thread_task_runner_;
@@ -166,13 +172,15 @@ DriGpuPlatformSupport::DriGpuPlatformSupport(
     DriWrapper* drm,
     DriWindowDelegateManager* window_manager,
     ScreenManager* screen_manager,
+    DriHelperThread* helper_thread,
     scoped_ptr<NativeDisplayDelegateDri> ndd)
     : sender_(NULL),
       drm_(drm),
       window_manager_(window_manager),
       screen_manager_(screen_manager),
       ndd_(ndd.Pass()) {
-  filter_ = new DriGpuPlatformSupportMessageFilter(window_manager, this);
+  filter_ = new DriGpuPlatformSupportMessageFilter(window_manager,
+                                                   helper_thread, this);
 }
 
 DriGpuPlatformSupport::~DriGpuPlatformSupport() {