cc: Remove SurfaceDependencies type

cc/surfaces/surface.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/surfaces/surface.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 202 matching lines @@
     // If a referenced surface does not have a corresponding active frame in the
     // display compositor, then it blocks this frame.
     if (!surface || !surface->HasActiveFrame())
       new_blocking_surfaces.insert(surface_id);
   }
 
   // If this Surface has a previous pending frame, then we must determine the
   // changes in dependencies so that we can update the SurfaceDependencyTracker
   // map.
   if (has_previous_pending_frame) {
-    SurfaceDependencies removed_dependencies;
+    base::flat_set<SurfaceId> removed_dependencies;
     for (const SurfaceId& surface_id : blocking_surfaces_) {
       if (!new_blocking_surfaces.count(surface_id))
         removed_dependencies.insert(surface_id);
     }
 
-    SurfaceDependencies added_dependencies;
+    base::flat_set<SurfaceId> added_dependencies;
     for (const SurfaceId& surface_id : new_blocking_surfaces) {
       if (!blocking_surfaces_.count(surface_id))
         added_dependencies.insert(surface_id);
     }
 
     // If there is a change in the dependency set, then inform observers.
     if (!added_dependencies.empty() || !removed_dependencies.empty()) {
       for (auto& observer : observers_) {
         observer.OnSurfaceDependenciesChanged(this, added_dependencies,
                                               removed_dependencies);
@@ skipping 106 matching lines @@
     frame->metadata.latency_info.swap(*latency_info);
     return;
   }
   std::copy(frame->metadata.latency_info.begin(),
             frame->metadata.latency_info.end(),
             std::back_inserter(*latency_info));
   frame->metadata.latency_info.clear();
 }
 
 }  // namespace cc