zero-copy: Clarify to allocate/destroy GpuMemoryBuffer on any thread and use it on the main thread o

ui/ozone/platform/drm/gbm_surface_factory.cc

Index: ui/ozone/platform/drm/gbm_surface_factory.cc
diff --git a/ui/ozone/platform/drm/gbm_surface_factory.cc b/ui/ozone/platform/drm/gbm_surface_factory.cc
index 290073bc3ba8166e13eccb1bd382565d013df1ec..d0f0273e5e47064e14177f9ac13d284fb31aaad1 100644
--- a/ui/ozone/platform/drm/gbm_surface_factory.cc
+++ b/ui/ozone/platform/drm/gbm_surface_factory.cc
@@ -74,6 +74,7 @@ GbmSurfaceFactory::GbmSurfaceFactory(bool allow_surfaceless)
 }
 
 GbmSurfaceFactory::~GbmSurfaceFactory() {
+  DCHECK(thread_checker_.CalledOnValidThread());
 }
 
 void GbmSurfaceFactory::InitializeGpu(DrmDeviceManager* drm_device_manager,
@@ -83,6 +84,7 @@ void GbmSurfaceFactory::InitializeGpu(DrmDeviceManager* drm_device_manager,
 }
 
 intptr_t GbmSurfaceFactory::GetNativeDisplay() {
+  DCHECK(thread_checker_.CalledOnValidThread());
 #if defined(USE_MESA_PLATFORM_NULL)
   return EGL_DEFAULT_DISPLAY;
 #else
@@ -93,6 +95,7 @@ intptr_t GbmSurfaceFactory::GetNativeDisplay() {
 }
 
 int GbmSurfaceFactory::GetDrmFd() {
+  DCHECK(thread_checker_.CalledOnValidThread());
   scoped_refptr<GbmDevice> gbm = GetGbmDevice(gfx::kNullAcceleratedWidget);
   DCHECK(gbm);
   return gbm->get_fd();
@@ -100,6 +103,7 @@ int GbmSurfaceFactory::GetDrmFd() {
 
 const int32* GbmSurfaceFactory::GetEGLSurfaceProperties(
     const int32* desired_list) {
+  DCHECK(thread_checker_.CalledOnValidThread());
   static const int32 kConfigAttribs[] = {EGL_BUFFER_SIZE,
                                          32,
                                          EGL_ALPHA_SIZE,
@@ -122,17 +126,20 @@ const int32* GbmSurfaceFactory::GetEGLSurfaceProperties(
 bool GbmSurfaceFactory::LoadEGLGLES2Bindings(
     AddGLLibraryCallback add_gl_library,
     SetGLGetProcAddressProcCallback set_gl_get_proc_address) {
+  DCHECK(thread_checker_.CalledOnValidThread());
   return LoadDefaultEGLGLES2Bindings(add_gl_library, set_gl_get_proc_address);
 }
 
 scoped_ptr<SurfaceOzoneCanvas> GbmSurfaceFactory::CreateCanvasForWidget(
     gfx::AcceleratedWidget widget) {
+  DCHECK(thread_checker_.CalledOnValidThread());
   LOG(FATAL) << "Software rendering mode is not supported with GBM platform";
   return nullptr;
 }
 
 scoped_ptr<SurfaceOzoneEGL> GbmSurfaceFactory::CreateEGLSurfaceForWidget(
     gfx::AcceleratedWidget widget) {
+  DCHECK(thread_checker_.CalledOnValidThread());
   scoped_refptr<GbmDevice> gbm = GetGbmDevice(widget);
   DCHECK(gbm);
 
@@ -147,6 +154,7 @@ scoped_ptr<SurfaceOzoneEGL> GbmSurfaceFactory::CreateEGLSurfaceForWidget(
 scoped_ptr<SurfaceOzoneEGL>
 GbmSurfaceFactory::CreateSurfacelessEGLSurfaceForWidget(
     gfx::AcceleratedWidget widget) {
+  DCHECK(thread_checker_.CalledOnValidThread());
   if (!allow_surfaceless_)
     return nullptr;
 
@@ -179,6 +187,7 @@ scoped_refptr<ui::NativePixmap> GbmSurfaceFactory::CreateNativePixmap(
 
 OverlayCandidatesOzone* GbmSurfaceFactory::GetOverlayCandidates(
     gfx::AcceleratedWidget w) {
+  DCHECK(thread_checker_.CalledOnValidThread());
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kOzoneTestSingleOverlaySupport))
     return new SingleOverlay();
@@ -192,6 +201,7 @@ bool GbmSurfaceFactory::ScheduleOverlayPlane(
     scoped_refptr<NativePixmap> buffer,
     const gfx::Rect& display_bounds,
     const gfx::RectF& crop_rect) {
+  DCHECK(thread_checker_.CalledOnValidThread());
   scoped_refptr<GbmPixmap> pixmap = static_cast<GbmPixmap*>(buffer.get());
   if (!pixmap.get()) {
     LOG(ERROR) << "ScheduleOverlayPlane passed NULL buffer.";
@@ -209,10 +219,12 @@ bool GbmSurfaceFactory::ScheduleOverlayPlane(
 }
 
 bool GbmSurfaceFactory::CanShowPrimaryPlaneAsOverlay() {
+  DCHECK(thread_checker_.CalledOnValidThread());
   return allow_surfaceless_;
 }
 
 bool GbmSurfaceFactory::CanCreateNativePixmap(BufferUsage usage) {
+  DCHECK(thread_checker_.CalledOnValidThread());
   switch (usage) {
     case MAP:
       return false;