New AudioTrack C++ API for audio timestamps

This new API is intended to replace latency(), especially for A/V sync.
The application will receive periodic timestamp notifications.  The period
is unspecified, but will likely be more frequent after a pause or stop,
set position, underrun, display on/off change, route change, or when audio
framework notices drift.  It will be up to the higher level application
(e.g.  Stagefright) to reconstruct a clock that updates more frequently.

The current latency() method doesn't indicate when latency changes
due to screen on/off state, route changes, etc.

Includes squahsed change-Id: I2082f8752040be0c234b1a6f1be2e269abf2ce7c
 Dummy implementation of AudioTrack:getTimestamp()
 Rename AudioTrack::Timestamp to AudioTimestamp.
 Renaming and pulling up to a higher level allows more modules to use it.

Change-Id: Ibf7f6a207c3f8d8697f25ede2cd5200697fadb86
(cherry picked from commit dd69eb893867634fd169c03204a6ad7c74b351e7)
diff --git a/include/media/AudioTimestamp.h b/include/media/AudioTimestamp.h
new file mode 100644
index 0000000..c29c7e5
--- /dev/null
+++ b/include/media/AudioTimestamp.h
@@ -0,0 +1,33 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ANDROID_AUDIO_TIMESTAMP_H
+#define ANDROID_AUDIO_TIMESTAMP_H
+
+#include <time.h>
+
+class AudioTimestamp {
+public:
+    AudioTimestamp() : mPosition(0) {
+        mTime.tv_sec = 0;
+        mTime.tv_nsec = 0;
+    }
+    // FIXME change type to match android.media.AudioTrack
+    uint32_t        mPosition; // a frame position in AudioTrack::getPosition() units
+    struct timespec mTime;     // corresponding CLOCK_MONOTONIC when frame is expected to present
+};
+
+#endif  // ANDROID_AUDIO_TIMESTAMP_H