[Hotword] Implement audio history pref accessing and setting.

chrome/browser/history/web_history_service.h

Index: chrome/browser/history/web_history_service.h
diff --git a/chrome/browser/history/web_history_service.h b/chrome/browser/history/web_history_service.h
index 692efbb0c0c4cc5ca84a34bcfb079b0d8b68ae20..309f4f499c4c825708d3201c1e7c4dd8d4478e6a 100644
--- a/chrome/browser/history/web_history_service.h
+++ b/chrome/browser/history/web_history_service.h
@@ -50,6 +50,9 @@ class WebHistoryService : public KeyedService {
 
   typedef base::Callback<void(bool success)> ExpireWebHistoryCallback;
 
+  typedef base::Callback<void(bool success, bool new_enabled_value)>
+      AudioWebHistoryCallback;
+
   explicit WebHistoryService(Profile* profile);
   ~WebHistoryService() override;
 
@@ -76,6 +79,12 @@ class WebHistoryService : public KeyedService {
                             base::Time end_time,
                             const ExpireWebHistoryCallback& callback);
 
+  // Requests whether audio history recording is enabled.
+  void GetAudioHistoryEnabled(const AudioWebHistoryCallback& callback);
+
+  // Sets the state of audio history recording to |new_enabled_value|.
+  void SetAudioHistoryEnabled(bool new_enabled_value,
+                              const AudioWebHistoryCallback& callback);
  private:
   // Called by |request| when a web history query has completed. Unpacks the
   // response and calls |callback|, which is the original callback that was
@@ -93,6 +102,14 @@ class WebHistoryService : public KeyedService {
       WebHistoryService::Request* request,
       bool success);
 
+  // Called by |request| when a request to get or set audio history from the
+  // server has completed. Unpacks the response and calls |callback|, which is
+  // the original callback that was passed to AudioHistory().
+  void AudioHistoryCompletionCallback(
+    const WebHistoryService::AudioWebHistoryCallback& callback,
+    WebHistoryService::Request* request,
+    bool success);
+
   Profile* profile_;
 
   // Stores the version_info token received from the server in response to
@@ -104,6 +121,9 @@ class WebHistoryService : public KeyedService {
   // shutdown.
   std::set<Request*> pending_expire_requests_;
 
+  // Pending requests to be canceled if not complete by profile shutdown.
+  std::set<Request*> pending_audio_history_requests_;
+
   base::WeakPtrFactory<WebHistoryService> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(WebHistoryService);