Add underlays and split off common overlay functionality

cc/output/overlay_strategy_underlay.cc

Index: cc/output/overlay_strategy_underlay.cc
diff --git a/cc/output/overlay_strategy_underlay.cc b/cc/output/overlay_strategy_underlay.cc
new file mode 100644
index 0000000000000000000000000000000000000000..c3242c20ca5df6d0a52b514db28d7e3578bcb351
--- /dev/null
+++ b/cc/output/overlay_strategy_underlay.cc
@@ -0,0 +1,86 @@
+// 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"
+#include "cc/quads/stream_video_draw_quad.h"
+#include "ui/gfx/geometry/rect_conversions.h"
+#include "ui/gfx/transform.h"
+
+namespace cc {
+
+OverlayStrategyUnderlay::OverlayStrategyUnderlay(
+    OverlayCandidateValidator* capability_checker,
+    ResourceProvider* resource_provider)
+    : OverlayStrategyCommon(resource_provider),
+      capability_checker_(capability_checker) {
+}
+
+bool OverlayStrategyUnderlay::IsOverlayQuad(const DrawQuad* draw_quad) {
+  switch (draw_quad->material) {
+    case DrawQuad::STREAM_VIDEO_CONTENT:

[alexst (slow to review), 2015/03/05 14:12:00]

We can allow WebGL here as well, I think.

[achaulk, 2015/03/18 16:31:26]

Done.

+      return resource_provider_->AllowOverlay(
+          StreamVideoDrawQuad::MaterialCast(draw_quad)->resource_id);
+    default:
+      return false;
+  }
+}
+
+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;
+  auto candidate_iterator = quad_list.end();
+  for (auto it = quad_list.begin(); it != quad_list.end(); ++it) {

[alexst (slow to review), 2015/03/05 14:12:00]

(auto it : quad_list) instead for simplicity?

+    const DrawQuad* draw_quad = *it;
+    if (IsOverlayQuad(draw_quad) &&
+        GetCandidateQuadInfo(*draw_quad, &candidate)) {
+      candidate_iterator = it;
+      break;
+    }
+  }
+  if (candidate_iterator == quad_list.end())
+    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;

[alexst (slow to review), 2015/03/05 14:12:00]

This should be -1 for the underlay.

+  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_iterator->shared_quad_state;
+    gfx::Rect rect = candidate_iterator->rect,
+              opaque = candidate_iterator->opaque_rect,

[alexst (slow to review), 2015/03/05 14:12:00]

If we are punching a hole, shouldn't opaque parts become transparent so we can
see through to the underlay? Or is there something in the quad constructor that
does that?

+              visible = candidate_iterator->visible_rect;
+    SolidColorDrawQuad* replacement =
+        new (*candidate_iterator) SolidColorDrawQuad();
+    replacement->SetAll(shared_quad_state, rect, opaque, visible, false,
+                        SK_ColorTRANSPARENT, true);

[halliwell, 2015/03/05 18:51:35]

I tried patching this change into my build this morning ... and what's here
doesn't actually seem to punch a transparent hole through to let the underlay
show.  If I change this to SK_ColorYELLOW, say, I can see the quad is getting
drawn in the right place, but with the code as it stands, the video area is just
black.

[achaulk, 2015/03/05 18:53:04]

Hmm, I just took the existing VIDEO_HOLE setup for the quad. Do you need
something more?

+    candidate_list->swap(candidates);
+    return true;
+  }
+  return false;
+}
+
+}  // namespace cc