Move some generic functions to AudioManagerBase to be inherited by platform-specific AudioManager***

media/audio/linux/alsa_output.cc

 // Copyright (c) 2012 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.
 //
 // THREAD SAFETY
 //
 // AlsaPcmOutputStream object is *not* thread-safe and should only be used
 // from the audio thread.  We DCHECK on this assumption whenever we can.
 //
 // SEMANTICS OF Close()
@@ skipping 277 matching lines @@
       alsa_buffer_frames_ = buffer_size;
     }
   }
 
   return true;
 }
 
 void AlsaPcmOutputStream::Close() {
   DCHECK(IsOnAudioThread());
 
-  // Sanity check that the transition occurs correctly.  It is safe to
-  // continue anyways because all operations for closing are idempotent.
-  if (TransitionTo(kIsClosed) != kIsClosed) {
-    NOTREACHED() << "Unable to transition Closed.";
-  } else {
-    // Shutdown the audio device.
-    if (playback_handle_ &&
-        alsa_util::CloseDevice(wrapper_, playback_handle_) < 0) {
+  if (state() != kIsClosed)
+    TransitionTo(kIsClosed);
+
+  // Shutdown the audio device.
+  if (playback_handle_) {
+    if (alsa_util::CloseDevice(wrapper_, playback_handle_) < 0) {
       LOG(WARNING) << "Unable to close audio device. Leaking handle.";
     }
     playback_handle_ = NULL;
 
     // Release the buffer.
     buffer_.reset();
 
     // Signal anything that might already be scheduled to stop.
     stop_stream_ = true;  // Not necessary in production, but unit tests
                           // uses the flag to verify that stream was closed.
-    weak_factory_.InvalidateWeakPtrs();
+  }
 
-    // Signal to the manager that we're closed and can be removed.
-    // Should be last call in the method as it deletes "this".
-    manager_->ReleaseOutputStream(this);
-  }
+  weak_factory_.InvalidateWeakPtrs();
+
+  // Signal to the manager that we're closed and can be removed.
+  // Should be last call in the method as it deletes "this".
+  manager_->ReleaseOutputStream(this);
 }
 
 void AlsaPcmOutputStream::Start(AudioSourceCallback* callback) {
   DCHECK(IsOnAudioThread());
 
   CHECK(callback);
 
   if (stop_stream_)
     return;
 
@@ skipping 513 matching lines @@
   if (source_callback_)
     source_callback_->OnError(this, code);
 }
 
 // Changes the AudioSourceCallback to proxy calls to.  Pass in NULL to
 // release ownership of the currently registered callback.
 void AlsaPcmOutputStream::set_source_callback(AudioSourceCallback* callback) {
   DCHECK(IsOnAudioThread());
   source_callback_ = callback;
 }