ozone: Allocate scanout buffer according to KMS modifiers

ui/ozone/platform/drm/gpu/drm_thread.cc

Index: ui/ozone/platform/drm/gpu/drm_thread.cc
diff --git a/ui/ozone/platform/drm/gpu/drm_thread.cc b/ui/ozone/platform/drm/gpu/drm_thread.cc
index 1b91c7eca2f8074ca60aef733c224e520e5bdeb1..a14724d8b31168b82f8606fa989b9ece5a8607da 100644
--- a/ui/ozone/platform/drm/gpu/drm_thread.cc
+++ b/ui/ozone/platform/drm/gpu/drm_thread.cc
@@ -124,8 +124,21 @@ void DrmThread::CreateBuffer(gfx::AcceleratedWidget widget,
       break;
   }
 
-  *buffer = GbmBuffer::CreateBuffer(
-      gbm, ui::GetFourCCFormatFromBufferFormat(format), size, flags);
+  DCHECK(screen_manager_);

[dnicoara, 2016/12/19 19:44:46]

nit: No need to DCHECK, the following access will just crash if screen_manager_
is nullptr. Also, the only reason this would be nullptr is if Init() wasn't run.

[hoegsberg1, 2016/12/22 23:05:20]

Acknowledged.

+  DrmWindow* window = screen_manager_->GetWindow(widget);
+  std::vector<uint64_t> modifiers;
+
+  uint32_t fourcc_format = ui::GetFourCCFormatFromBufferFormat(format);
+
+  if (window && window->GetController())

[Daniele Castagna, 2016/12/20 18:03:28]

It'd be nice to understand why this happens, or at least leave a comment
mentioning we need to investigate further.
I don't think it's related to the logout button race we observed, since that one
was about adding ui elements.

[hoegsberg1, 2016/12/22 23:05:20]

I added a todo there.

+    modifiers = window->GetController()->GetFormatModifiers(fourcc_format);
+
+  if (modifiers.size() > 0 && !(flags & GBM_BO_USE_LINEAR)) {
+    *buffer = GbmBuffer::CreateBufferWithModifiers(gbm, fourcc_format, size,
+                                                   flags, modifiers);
+  } else {
+    *buffer = GbmBuffer::CreateBuffer(gbm, fourcc_format, size, flags);
+  }
 }
 
 void DrmThread::CreateBufferFromFds(