Introduce MediaDevicesPermissionChecker.

content/browser/media/media_devices_permission_checker.h

Index: content/browser/media/media_devices_permission_checker.h
diff --git a/content/browser/media/media_devices_permission_checker.h b/content/browser/media/media_devices_permission_checker.h
new file mode 100644
index 0000000000000000000000000000000000000000..7ac95c89c799448b1cc0b0aed15a30c6e7c54742
--- /dev/null
+++ b/content/browser/media/media_devices_permission_checker.h
@@ -0,0 +1,86 @@
+// 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_

[xhwang, 2016/10/28 17:14:56]

OOC, can we put this file in content/browser/renderer_host/media/ since this is
only used for "renderer host"?

[Guido Urdaneta, 2016/10/29 19:34:38]

That would be my preference, but the .cc includes "content/browser/frame_host",
and it is forbidden to include that directory from
"content/browser/renderer_host/media".
Any workaround?

[xhwang, 2016/10/30 16:18:27]

I see. I am not familiar with this part. A content/ owner should know.

+#define CONTENT_BROWSER_MEDIA_MEDIA_DEVICES_PERMISSION_CHECKER_H_
+
+#include <memory>
+
+#include "base/callback.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 has various utility functions to check if a render frame

[xhwang, 2016/10/28 17:14:56]

"provides has"?

[Guido Urdaneta, 2016/10/29 19:34:38]

Done.

+// has permission to access media devices. Note that none of the methods
+// prompts the user to request permission.
+class CONTENT_EXPORT MediaDevicesPermissionChecker {
+ public:
+  MediaDevicesPermissionChecker();
+
+  // Checks if the origin |security_origin| associated to a render frame
+  // identified by |render_process_id| and |routing_id| is allowed to access
+  // the media device type |device_type|.
+  // This method must be called on the UI thread.
+  bool CheckPermission(MediaDeviceType device_type,

[xhwang, 2016/10/28 17:14:56]

Does this make sense to name this CheckPermissionOnUIThread?

https://google.github.io/styleguide/cppguide.html#Function_Overloading

[Guido Urdaneta, 2016/10/29 19:34:37]

Done.

+                       int render_process_id,
+                       int routing_id,

[xhwang, 2016/10/28 17:14:56]

It seems less ambiguouse to use render_frame_id when we are out of RenderFrame*
context:

https://cs.chromium.org/search/?q=render_frame_id&sq=package:chromium&type=cs

[Guido Urdaneta, 2016/10/29 19:34:37]

Done.

+                       const url::Origin& security_origin);
+
+  // Checks if the origin |security_origin| associated to a render frame
+  // identified by |render_process_id| and |routing_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.

[xhwang, 2016/10/28 17:14:56]

nit: might worth commenting that the |callback| will always be fired on the
thread this method is called on.

[Guido Urdaneta, 2016/10/29 19:34:38]

Done.

+  void CheckPermission(MediaDeviceType device_type,
+                       int render_process_id,
+                       int routing_id,
+                       const url::Origin& security_origin,
+                       const base::Callback<void(bool)>& callback);
+
+  // Checks if the origin |security_origin| associated to a render frame
+  // identified by |render_process_id| and |routing_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 CheckPermissions(
+      MediaDevicesManager::BoolDeviceTypes requested_device_types,
+      int render_process_id,
+      int routing_id,
+      const url::Origin& security_origin);
+
+  // Checks if the origin |security_origin| associated to a render frame
+  // identified by |render_process_id| and |routing_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.
+  void CheckPermissions(
+      MediaDevicesManager::BoolDeviceTypes requested_device_types,
+      int render_process_id,
+      int routing_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.
+  void OverridePermissions(bool override_value);

[xhwang, 2016/10/28 17:14:56]

Could you please document the use case for this? It's a bit odd to override
permission values.

[Guido Urdaneta, 2016/10/29 19:34:37]

Done. Renamed the method to OverridePermissionForTesting.

+
+ private:
+  bool use_override_;
+  bool override_value_;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_MEDIA_MEDIA_DEVICES_PERMISSION_CHECKER_H_