Fix audio capture buffer handling on Android.

The buffer handling in OpenSL is:
1. enqueue the buffers;
2. wait for a callback;
3. inside the callback, read out the PCM data of current buffer and enqueue one buffer (it's the same buffer in this case).
4. go to step 2.

Current implementation has several problems:
a. When buffer #1 (not buffer #0) is read first time, it doesn't have PCM data recorded by the device. 
b. There are 2 buffer worth of time delay.
c. There are racing condtion since both OpenSL and AudioInputController hold the same buffer.

BUG=243506
R=xians@chromium.org

Review URL: https://codereview.chromium.org/15941002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@202581 0039d316-1c4b-4281-b951-d872f2087c98

media/audio/android/opensles_input.cc

@@ -71,7 +71,7 @@ void OpenSLESInputStream::Start(AudioInputCallback* callback) {
 
   SLresult err = SL_RESULT_UNKNOWN_ERROR;
   // Enqueues |kNumOfQueuesInBuffer| zero buffers to get the ball rolling.
-  for (int i = 0; i < kNumOfQueuesInBuffer - 1; ++i) {
+  for (int i = 0; i < kNumOfQueuesInBuffer; ++i) {
     err = (*simple_buffer_queue_)->Enqueue(
         simple_buffer_queue_,
         audio_data_[i],
@@ -187,7 +187,7 @@ bool OpenSLESInputStream::CreateRecorder() {
 
   // Audio sink configuration.
   SLDataLocator_AndroidSimpleBufferQueue buffer_queue = {
-    SL_DATALOCATOR_ANDROIDSIMPLEBUFFERQUEUE, // Locator type.
+    SL_DATALOCATOR_ANDROIDSIMPLEBUFFERQUEUE,  // Locator type.
     static_cast<SLuint32>(kNumOfQueuesInBuffer)  // Number of buffers.
   };
   SLDataSink audio_sink = { &buffer_queue, &format_ };
@@ -258,14 +258,6 @@ void OpenSLESInputStream::ReadBufferQueue() {
   if (!started_)
     return;
 
-  // Get the enqueued buffer from the soundcard.
-  SLresult err = (*simple_buffer_queue_)->Enqueue(
-      simple_buffer_queue_,
-      audio_data_[active_queue_],
-      buffer_size_bytes_);
-  if (SL_RESULT_SUCCESS != err)
-    HandleError(err);
-
   // TODO(xians): Get an accurate delay estimation.
   callback_->OnData(this,
                     audio_data_[active_queue_],
@@ -273,6 +265,14 @@ void OpenSLESInputStream::ReadBufferQueue() {
                     buffer_size_bytes_,
                     0.0);
 
+  // Done with this buffer. Send it to device for recording.
+  SLresult err = (*simple_buffer_queue_)->Enqueue(
+      simple_buffer_queue_,
+      audio_data_[active_queue_],
+      buffer_size_bytes_);
+  if (SL_RESULT_SUCCESS != err)
+    HandleError(err);
+
   active_queue_ = (active_queue_ + 1) % kNumOfQueuesInBuffer;
 }