Move ReferencedSurfaceTracker into GpuCompositorFrameSink.

cc/surfaces/referenced_surface_tracker.cc

+// Copyright 2016 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/surfaces/referenced_surface_tracker.h"
+
+#include <utility>
+
+#include "base/logging.h"
+
+namespace cc {
+
+ReferencedSurfaceTracker::ReferencedSurfaceTracker(
+    const FrameSinkId& frame_sink_id)
+    : current_surface_id_(frame_sink_id, LocalFrameId()) {
+  DCHECK(current_surface_id_.frame_sink_id().is_valid());
+}
+
+ReferencedSurfaceTracker::~ReferencedSurfaceTracker() {}
+
+void ReferencedSurfaceTracker::UpdateReferences(
+    const LocalFrameId& local_frame_id,
+    const std::vector<SurfaceId>& referenced_surfaces) {
+  DCHECK(local_frame_id.is_valid());
+
+  // Clear references to add/remove from the last frame.
+  references_to_remove_.clear();
+  references_to_add_.clear();
+
+  // If |current_surface_id_| is changing then update |current_surface_id_|.
+  // Also clear |referenced_surfaces_| because we haven't added any references
+  // from the new SurfaceId yet.
+  if (current_surface_id_.local_frame_id() != local_frame_id) {
+    current_surface_id_ =
+        SurfaceId(current_surface_id_.frame_sink_id(), local_frame_id);
+    referenced_surfaces_.clear();
+  }
+
+  UpdateReferencedSurfaces(referenced_surfaces);
+}
+
+void ReferencedSurfaceTracker::UpdateReferencedSurfaces(
+    const std::vector<SurfaceId>& new_referenced_surfaces) {
+  std::unordered_set<SurfaceId, SurfaceIdHash> new_referenced_surfaces_set;
+
+  // Add references for each SurfaceId in |new_referenced_surfaces| if they
+  // aren't already referenced.

[Fady Samuel, 2017/01/18 01:08:55]

Can you use std::set_difference?

[kylechar, 2017/01/18 15:20:15]

It's possible but I don't think the right solution. It's more code than the for
loop and it produces extra copies, since set_difference needs a temporary
collection to output to that will get destroyed at the end of the method. I
cleaned this up a bit to make it more understandable though.

+  for (const SurfaceId& surface_id : new_referenced_surfaces) {
+    ReferenceSurface(surface_id);
+    new_referenced_surfaces_set.insert(surface_id);
+  }
+
+  // Check for SurfaceIds that are no longer referenced and remove them.
+  for (const SurfaceId& surface_id : referenced_surfaces_) {
+    if (new_referenced_surfaces_set.count(surface_id) == 0)
+      UnreferenceSurface(surface_id);
+  }
+}
+
+void ReferencedSurfaceTracker::ReferenceSurface(const SurfaceId& surface_id) {
+  // If we already have a reference to |surface_id| then return early.
+  if (referenced_surfaces_.count(surface_id) > 0)
+    return;
+
+  // Record that surface is referenced and add a reference.
+  references_to_add_.push_back(
+      SurfaceReference(current_surface_id_, surface_id));
+  referenced_surfaces_.insert(surface_id);
+}
+
+void ReferencedSurfaceTracker::UnreferenceSurface(const SurfaceId& surface_id) {
+  auto iter = referenced_surfaces_.find(surface_id);
+  if (iter == referenced_surfaces_.end())
+    return;
+
+  // Remove record that surface is referenced and remove reference.
+  references_to_remove_.push_back(
+      SurfaceReference(current_surface_id_, surface_id));
+  referenced_surfaces_.erase(iter);
+}
+
+}  // namespace cc