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) {
+  // If a buffer is too big, buffer allocation for scanout will fail.

[dnicoara, 2017/02/21 19:03:18]

Since we're expecting the AddFramebuffer2() call to fail, perhaps use
MockDrmDevice::set_add_framebuffer_expectation(false) to trigger the fail (and
not some arbitrary size). That should be the same scenario we're currently
experiencing on devices, right?

[Daniele Castagna, 2017/02/21 19:12:21]

You're right that what you described is the scenario we're trying to deal with.

We're never calling AddFramebuffer in these tests though.
We just call MockScanoutBufferGenerator::Create that creates a mock buffer.

We could use something like
MockScanoutBufferGenerator::set_allocation_failure(true)?
What do you think?

[dnicoara, 2017/02/21 19:19:39]

Oh, you're right, that makes me feel a bit sad :(
Yeah, this sounds better. Less chance of accidentally breaking other tests.

+  // In that case we should reject the overlay candidate.
+  ui::OverlayCheck_Params too_big_candidate;
+
+  too_big_candidate.buffer_size = gfx::Size(4800, 3200);
+  too_big_candidate.display_rect = primary_rect_;
+  std::vector<ui::OverlayCheck_Params> overlay_params;
+  overlay_params.push_back(too_big_candidate);
+
+  std::vector<ui::OverlayCheck_Params> validated_params =
+      overlay_validator_->TestPageFlip(overlay_params, ui::OverlayPlaneList());
+  EXPECT_FALSE(validated_params.front().is_overlay_candidate);
+}