Fix use after free for cached_displays_.

ui/ozone/platform/drm/host/drm_display_host_manager.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 "ui/ozone/platform/drm/host/drm_display_host_manager.h"
 
 #include <fcntl.h>
 #include <stddef.h>
 #include <xf86drm.h>
 
@@ skipping 341 matching lines @@
     GpuRelinquishedDisplayControl(false);
 
   device_manager_->ScanDevices(this);
   NotifyDisplayDelegate();
 }
 
 void DrmDisplayHostManager::OnGpuThreadRetired() {}
 
 void DrmDisplayHostManager::GpuHasUpdatedNativeDisplays(
     const std::vector<DisplaySnapshot_Params>& params) {
+  if (delegate_)
+    delegate_->OnDisplaySnapshotsInvalidated();
   std::vector<std::unique_ptr<DrmDisplayHost>> old_displays;
   displays_.swap(old_displays);
   for (size_t i = 0; i < params.size(); ++i) {
     auto it = std::find_if(old_displays.begin(), old_displays.end(),
                            FindDrmDisplayHostById(params[i].display_id));
     if (it == old_displays.end()) {
       displays_.push_back(base::MakeUnique<DrmDisplayHost>(
           proxy_, params[i], false /* is_dummy */));
     } else {
       (*it)->UpdateDisplaySnapshot(params[i]);
@@ skipping 87 matching lines @@
 
   callback.Run(snapshots);
 }
 
 void DrmDisplayHostManager::NotifyDisplayDelegate() const {
   if (delegate_)
     delegate_->OnConfigurationChanged();
 }
 
 }  // namespace ui