Fix race in MediaDevicesPermissionChecker.

content/browser/media/media_devices_permission_checker.h

 // 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.
 
 #ifndef CONTENT_BROWSER_MEDIA_MEDIA_DEVICES_PERMISSION_CHECKER_H_
 #define CONTENT_BROWSER_MEDIA_MEDIA_DEVICES_PERMISSION_CHECKER_H_
 
 #include <memory>
 
 #include "base/callback.h"
+#include "base/macros.h"
 #include "content/browser/renderer_host/media/media_devices_manager.h"
 #include "content/common/content_export.h"
 
 namespace url {
 class Origin;
 }
 
 namespace content {
 
 // This class provides various utility functions to check if a render frame
 // has permission to access media devices. Note that none of the methods
 // prompts the user to request permission.
 class CONTENT_EXPORT MediaDevicesPermissionChecker {
  public:
   MediaDevicesPermissionChecker();
+  // This constructor creates a MediaDevicesPermissionChecker that replies
+  // |override_value| to all permission requests. Use only for testing.
+  explicit MediaDevicesPermissionChecker(bool override_value);
 
   // Checks if the origin |security_origin| associated to a render frame
   // identified by |render_process_id| and |render_frame_id| is allowed to
   // access the media device type |device_type|.
   // This method must be called on the UI thread.
   bool CheckPermissionOnUIThread(MediaDeviceType device_type,
                                  int render_process_id,
                                  int render_frame_id,
-                                 const url::Origin& security_origin);
+                                 const url::Origin& security_origin) const;
 
   // Checks if the origin |security_origin| associated to a render frame
   // identified by |render_process_id| and |render_frame_id| is allowed to
   // access the media device type |device_type|. The result is passed to
   // |callback|.
   // This method can be called on any thread. |callback| is fired on the same
   // thread this method is called on.
   void CheckPermission(MediaDeviceType device_type,
                        int render_process_id,
                        int render_frame_id,
                        const url::Origin& security_origin,
-                       const base::Callback<void(bool)>& callback);
+                       const base::Callback<void(bool)>& callback) const;
 
   // Checks if the origin |security_origin| associated to a render frame
   // identified by |render_process_id| and |render_frame_id| is allowed to
   // access the media device types marked with a value of true in
   // |requested_device_types|.  The result is indexed by MediaDeviceType.
   // Entries in the result with a value of true for requested device types
   // indicate that the frame has permission to access devices of the
   // corresponding types.
   // This method must be called on the UI thread.
   MediaDevicesManager::BoolDeviceTypes CheckPermissionsOnUIThread(
       MediaDevicesManager::BoolDeviceTypes requested_device_types,
       int render_process_id,
       int render_frame_id,
-      const url::Origin& security_origin);
+      const url::Origin& security_origin) const;
 
   // Checks if the origin |security_origin| associated to a render frame
   // identified by |render_process_id| and |render_frame_id| is allowed to
   // access the media device types marked with a value of true in
   // |requested_device_types|. The result is passed to |callback|. The result is
   // indexed by MediaDeviceType. Entries in the result with a value of true for
   // requested  device types indicate that the frame has permission to access
   // devices of the corresponding types.
   // This method can be called on any thread. |callback| is fired on the same
   // thread this method is called on.
   void CheckPermissions(
       MediaDevicesManager::BoolDeviceTypes requested_device_types,
       int render_process_id,
       int render_frame_id,
       const url::Origin& security_origin,
       const base::Callback<void(const MediaDevicesManager::BoolDeviceTypes&)>&
-          callback);
-
-  // Forces a specific value to be returned by the permission-checking functions
-  // for all device types. Use only for testing.
-  void OverridePermissionsForTesting(bool override_value);
+          callback) const;
 
  private:
-  bool use_override_;
-  bool override_value_;
+  const bool use_override_;
+  const bool override_value_;
+
+  DISALLOW_COPY_AND_ASSIGN(MediaDevicesPermissionChecker);

[Max Morin, 2016/11/03 13:57:40]

Wouldn't it be easier to just allow copies so you don't need to wrap it in a
unique_ptr?

 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_MEDIA_MEDIA_DEVICES_PERMISSION_CHECKER_H_