Add underlays and split off common overlay functionality

cc/output/overlay_strategy_underlay.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 "cc/output/overlay_strategy_underlay.h"
+
+#include "cc/quads/draw_quad.h"
+#include "cc/quads/solid_color_draw_quad.h"
+
+namespace cc {
+
+OverlayStrategyUnderlay::OverlayStrategyUnderlay(
+    OverlayCandidateValidator* capability_checker,
+    ResourceProvider* resource_provider)
+    : OverlayStrategyCommon(capability_checker, resource_provider) {
+}
+
+bool OverlayStrategyUnderlay::Attempt(
+    RenderPassList* render_passes_in_draw_order,
+    OverlayCandidateList* candidate_list) {
+  if (!capability_checker_)
+    return false;
+
+  RenderPass* root_render_pass = render_passes_in_draw_order->back();
+  DCHECK(root_render_pass);
+
+  OverlayCandidate candidate;
+  QuadList& quad_list = root_render_pass->quad_list;
+  DrawQuad* candidate_quad = nullptr;
+  for (auto* draw_quad : quad_list) {
+    if (IsOverlayQuad(draw_quad) &&
+        GetCandidateQuadInfo(*draw_quad, &candidate)) {
+      candidate_quad = draw_quad;
+      break;
+    }
+  }
+  if (!candidate_quad)
+    return false;
+
+  // Add our primary surface.
+  OverlayCandidateList candidates;
+  OverlayCandidate main_image;
+  main_image.display_rect = root_render_pass->output_rect;
+  candidates.push_back(main_image);
+
+  // Add the overlay.
+  candidate.plane_z_order = -1;
+  candidates.push_back(candidate);
+
+  // Check for support.
+  capability_checker_->CheckOverlaySupport(&candidates);
+
+  // If the candidate can be handled by an overlay, create a pass for it. We
+  // need to switch out the video quad with a black transparent one.
+  if (candidates[1].overlay_handled) {
+    const SharedQuadState* shared_quad_state =
+        candidate_quad->shared_quad_state;
+    gfx::Rect rect = candidate_quad->visible_rect;
+    SolidColorDrawQuad* replacement = new (candidate_quad) SolidColorDrawQuad();

[danakj, 2015/03/18 21:30:14]

I think we should do this by adding a replace type method of the QuadList
allocator. This is pretty unclear why it would always work, and doesn't feel
reliable for all time.

[achaulk, 2015/03/23 19:16:03]

Yeah, that's probably a good idea. It does depend on the quad list
implementation

+    replacement->SetAll(shared_quad_state, rect, rect, rect, false,
+                        SK_ColorTRANSPARENT, true);
+    candidate_list->swap(candidates);
+    return true;
+  }
+  return false;
+}
+
+}  // namespace cc