[ios] Adds support for parsing Text-to-Speech search results.

ios/chrome/browser/ui/voice/text_to_speech_player.h

+// 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 IOS_CHROME_BROWSER_UI_VOICE_TEXT_TO_SPEECH_PLAYER_H_
+#define IOS_CHROME_BROWSER_UI_VOICE_TEXT_TO_SPEECH_PLAYER_H_
+
+#import <Foundation/Foundation.h>
+
+// Class responsible for playing TextToSpeech audio data and emitting audio
+// levels.
+@interface TextToSpeechPlayer : NSObject
+
+// Whether there is audio data prepared to be played.
+@property(nonatomic, readonly, getter=isReadyForPlayback) BOOL readyForPlayback;
+
+// Whether the TextToSpeechPlayer is currently playing audio.
+@property(nonatomic, readonly, getter=isPlayingAudio) BOOL playingAudio;
+
+// Stores a reference to |audioData| and clears up prior TTS state.  Calling
+// this function while |playingAudio| is YES will cancel prior playback.  This
+// function will post a kTTSAudioReadyForPlaybackNotification notification with
+// the TexToSpeechPlayer used as the sending object.
+- (void)prepareToPlayAudioData:(NSData*)audioData;
+
+// Creates an AVAudioPlayer and begins playing audio data passed to
+// |-prepareToPlayAudioData:|.  no-op if called when |readyForPlayback| is NO

[sdefresne, 2016/10/25 13:20:30]

Should this be spelled "No-op" as it is starting a sentence?

[rohitrao (ping after 24h), 2016/10/25 15:23:12]

Done.

+// or |playingAudio| is YES.  This function will post a
+// kTTSWillStartPlayingNotification with the TextToSpeechPlayer used as the
+// sending object.
+- (void)beginPlayback;
+
+// Stops any active playback and notifies observers that TTS has stopped.  This
+// function will post a kTTSDidStopPlayingNotification notification with the
+// TextToSpeechPlayer used as the sending object.
+- (void)cancelPlayback;
+
+@end
+
+#endif  // IOS_CHROME_BROWSER_UI_VOICE_TEXT_TO_SPEECH_PLAYER_H_