Retain references to surfaces from both active AND pending CompositorFrames

cc/surfaces/surface_dependency_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/surface_dependency_tracker.h"
 
 #include "cc/surfaces/surface.h"
 #include "cc/surfaces/surface_info.h"
 #include "cc/surfaces/surface_manager.h"
 
 namespace cc {
 
 namespace {
 constexpr uint32_t kMaxBeginFrameCount = 4;
 }
 
 SurfaceDependencyTracker::SurfaceDependencyTracker(
     SurfaceManager* surface_manager,
     BeginFrameSource* begin_frame_source)
     : surface_manager_(surface_manager),
       begin_frame_source_(begin_frame_source) {
   surface_manager_->AddObserver(this);
   begin_frame_source_->AddObserver(this);
 }
 
 SurfaceDependencyTracker::~SurfaceDependencyTracker() {
   surface_manager_->RemoveObserver(this);
   begin_frame_source_->RemoveObserver(this);
+  for (Surface* pending_surface : pending_surfaces_)
+    pending_surface->RemoveObserver(this);
+  pending_surfaces_.clear();
 }
 
 void SurfaceDependencyTracker::RequestSurfaceResolution(Surface* surface) {
   DCHECK(surface->HasPendingFrame());
 
   const CompositorFrame& pending_frame = surface->GetPendingFrame();
   bool needs_begin_frame =
       pending_frame.metadata.can_activate_before_dependencies;
 
   // Referenced surface IDs that aren't currently known to the surface manager
@@ skipping 132 matching lines @@
   // have a deadline.
   if (blocked_surfaces_.empty())
     frames_since_deadline_set_.reset();
 
   // Tell each surface about the availability of its blocker.
   for (Surface* blocked_pending_surface : blocked_pending_surface_set)
     blocked_pending_surface->NotifySurfaceIdAvailable(surface_id);
 }
 
 }  // namespace cc