ozone/drm: Only reuse ScanoutBuffers with compatible modifiers

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

Index: ui/ozone/platform/drm/gpu/screen_manager.cc
diff --git a/ui/ozone/platform/drm/gpu/screen_manager.cc b/ui/ozone/platform/drm/gpu/screen_manager.cc
index 5dd26663881c04668e11dd0a4af17bb746c38dfb..ee58fa406dd8af12fae8c794a1f9a40744388fe9 100644
--- a/ui/ozone/platform/drm/gpu/screen_manager.cc
+++ b/ui/ozone/platform/drm/gpu/screen_manager.cc
@@ -348,17 +348,32 @@ OverlayPlane ScreenManager::GetModesetBuffer(
     HardwareDisplayController* controller,
     const gfx::Rect& bounds) {
   DrmWindow* window = FindWindowAt(bounds);
+
+  gfx::BufferFormat format = display::DisplaySnapshot::PrimaryFormat();
+  uint32_t fourcc_format = ui::GetFourCCFormatForOpaqueFramebuffer(format);
+
   if (window) {
     const OverlayPlane* primary = window->GetLastModesetBuffer();
     const DrmDevice* drm = controller->GetAllocationDrmDevice().get();
     if (primary && primary->buffer->GetSize() == bounds.size() &&
-        primary->buffer->GetDrmDevice() == drm)
-      return *primary;
+        primary->buffer->GetDrmDevice() == drm) {
+
+      // If the controller doesn't advertise modifiers, wont have a
+      // modifier either and we can reuse the buffer. Otherwise, check
+      // to see if the controller supports the buffers format
+      // modifier.
+      const auto& modifiers = controller->GetFormatModifiers(fourcc_format);
+      if (modifiers.size() == 0)

[Daniele Castagna, 2017/06/03 19:53:06]

nit: !modifiers.size()

[dnicoara, 2017/06/05 15:54:58]

Actually, use: modifiers.empty()

+        return *primary;
+      for (const uint64_t modifier : modifiers) {

[Daniele Castagna, 2017/06/03 19:53:05]

You could use std::find here. I have no preference.

+        if (modifier == primary->buffer->GetFormatModifier()) {

[Daniele Castagna, 2017/06/03 19:53:06]

nit: curly braces not needed.

+          return *primary;
+        }
+      }
+    }
   }
 
-  gfx::BufferFormat format = display::DisplaySnapshot::PrimaryFormat();
   scoped_refptr<DrmDevice> drm = controller->GetAllocationDrmDevice();
-  uint32_t fourcc_format = ui::GetFourCCFormatForOpaqueFramebuffer(format);
   scoped_refptr<ScanoutBuffer> buffer =
       buffer_generator_->Create(drm, fourcc_format, bounds.size());
   if (!buffer) {