ozone: Add overlay candidate implementation that queries support via IPC

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

 // Copyright 2014 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_window.h"
 
 #include "base/trace_event/trace_event.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "third_party/skia/include/core/SkDevice.h"
 #include "third_party/skia/include/core/SkSurface.h"
 #include "ui/ozone/platform/drm/gpu/drm_buffer.h"
 #include "ui/ozone/platform/drm/gpu/drm_device.h"
 #include "ui/ozone/platform/drm/gpu/drm_device_manager.h"
 #include "ui/ozone/platform/drm/gpu/screen_manager.h"
 
 namespace ui {
 
 namespace {
 
 #ifndef DRM_CAP_CURSOR_WIDTH
 #define DRM_CAP_CURSOR_WIDTH 0x8
 #endif
 
 #ifndef DRM_CAP_CURSOR_HEIGHT
 #define DRM_CAP_CURSOR_HEIGHT 0x9
 #endif
 
+void EmptyFlipCallback(gfx::SwapResult) {
+}
+
 void UpdateCursorImage(DrmBuffer* cursor, const SkBitmap& image) {
   SkRect damage;
   image.getBounds(&damage);
 
   // Clear to transparent in case |image| is smaller than the canvas.
   SkCanvas* canvas = cursor->GetCanvas();
   canvas->clear(SK_ColorTRANSPARENT);
 
   SkRect clip;
   clip.set(0, 0, canvas->getDeviceSize().width(),
@@ skipping 94 matching lines @@
 
   if (controller_) {
     return controller_->SchedulePageFlip(last_submitted_planes_, is_sync, false,
                                          callback);
   }
 
   callback.Run(gfx::SwapResult::SWAP_ACK);
   return true;
 }
 
+bool DrmWindow::TestPageFlip(const OverlayPlaneList& planes) {
+  return controller_ &&

[spang, 2015/06/01 19:47:39]

Shouldn't it be

if (!controller_)
  return true;

Flipping an offscreen window is an no-op and cannot fail no matter how many
overlays we have. No point in doing any composition.

[achaulk, 2015/06/01 20:43:08]

Sure? It doesn't really matter what we return

+         controller_->SchedulePageFlip(last_submitted_planes_, true, true,
+                                       base::Bind(&EmptyFlipCallback));
+}
+
 const OverlayPlane* DrmWindow::GetLastModesetBuffer() {
   return OverlayPlane::GetPrimaryPlane(last_submitted_planes_);
 }
 
 void DrmWindow::ResetCursor(bool bitmap_only) {
   if (!controller_)
     return;
 
   if (cursor_bitmaps_.size()) {
     // Draw new cursor into backbuffer.
@@ skipping 53 matching lines @@
       if (!cursor_buffers_[i]->Initialize(
               info, false /* should_register_framebuffer */)) {
         LOG(FATAL) << "Failed to initialize cursor buffer";
         return;
       }
     }
   }
 }
 
 }  // namespace ui