cast: Support for low-latency interactive mode

content/browser/media/capture/ui_activity_tracker.h

Index: content/browser/media/capture/ui_activity_tracker.h
diff --git a/content/browser/media/capture/ui_activity_tracker.h b/content/browser/media/capture/ui_activity_tracker.h
new file mode 100644
index 0000000000000000000000000000000000000000..5a512c6c99d410e71708b1fa3c284db3e7a68cdb
--- /dev/null
+++ b/content/browser/media/capture/ui_activity_tracker.h
@@ -0,0 +1,32 @@
+// Copyright (c) 2015 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_CAPTURE_UI_ACTIVITY_TRACKER_H_
+#define CONTENT_BROWSER_MEDIA_CAPTURE_UI_ACTIVITY_TRACKER_H_
+
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "content/common/content_export.h"
+
+namespace content {
+
+// UiActivityTracker is an interface that can be implememented to report
+// whether the user is actively interacting with UI.
+class CONTENT_EXPORT UiActivityTracker {

[miu, 2015/12/03 21:26:22]

naming nit: Based on what this does, consider something like
WindowActivityTracker.

[Irfan, 2015/12/04 22:45:37]

Done.

+ public:
+  virtual ~UiActivityTracker() {}
+
+  // Returns true if UI interaction is active.
+  virtual bool uiInteractionActive() const = 0;

[miu, 2015/12/03 21:26:22]

style: No camel case.  Suggestion: IsUiInteractionActive() or
IsUserInteracting()

[Irfan, 2015/12/04 22:45:37]

Done.

+
+  // Resets any previous UI activity tracked.
+  virtual void reset() = 0;

[miu, 2015/12/03 21:26:22]

Because it's non-inlined (and virtual), style requires: Reset()

[Irfan, 2015/12/04 22:45:37]

Done.

+
+  // Returns a weak pointer.
+  virtual base::WeakPtr<UiActivityTracker> GetWeakPtr() = 0;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_MEDIA_CAPTURE_UI_ACTIVITY_TRACKER_H_