ozone: Reject overlays when a test buffer can't be allocated.

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

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/ozone/platform/drm/gpu/drm_overlay_validator.h"
 
 #include <drm_fourcc.h>
 
 #include <memory>
 #include <utility>
@@ skipping 610 matching lines @@
             plane_list.back().buffer->GetFramebufferPixelFormat());
   plane_list_.back().processing_callback = base::Bind(
       &DrmOverlayValidatorTest::ReturnNullBuffer, base::Unretained(this));
 
   plane_list = overlay_validator_->PrepareBuffersForPageFlip(plane_list_);
   EXPECT_EQ(plane_list_.back().buffer->GetFramebufferPixelFormat(),
             plane_list.back().buffer->GetFramebufferPixelFormat());
   plane_list_.back().processing_callback = base::Bind(
       &DrmOverlayValidatorTest::ProcessBuffer, base::Unretained(this));
 }
+
+TEST_F(DrmOverlayValidatorTest, RejectBufferAllocationFail) {
+  // Buffer allocation for scanout might fail.
+  // In that case we should reject the overlay candidate.
+  buffer_generator_->set_allocation_failure(true);
+
+  std::vector<ui::OverlayCheck_Params> validated_params =
+      overlay_validator_->TestPageFlip(overlay_params_, ui::OverlayPlaneList());
+  EXPECT_FALSE(validated_params.front().is_overlay_candidate);
+}