Chromecast: provides a method to check if config has been set by user.

R=lcwu@chromium.org,byungchul@chromium.org
BUG=None

Review URL: https://codereview.chromium.org/603243003

Cr-Commit-Position: refs/heads/master@{#296971}

chromecast/common/chromecast_config.cc

@@ -138,4 +138,9 @@ void ChromecastConfig::SetIntValue(const std::string& key, int value) const {
   }
 }
 
+bool ChromecastConfig::HasValue(const std::string& key) const {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  return pref_service_->HasPrefPath(key.c_str());
+}
+
 }  // namespace chromecast

chromecast/common/chromecast_config.h

@@ -37,18 +37,21 @@ class ChromecastConfig {
   // Saves configs into configuration file.
   void Save() const;
 
-  // Returns string value for key, if present.
+  // Returns string value for |key|, if present.
   const std::string GetValue(const std::string& key) const;
 
-  // Returns integer value for key, if present.
+  // Returns integer value for |key|, if present.
   const int GetIntValue(const std::string& key) const;
 
-  // Sets new string value for key.
+  // Sets new string value for |key|.
   void SetValue(const std::string& key, const std::string& value) const;
 
-  // Sets new int value for key.
+  // Sets new int value for |key|.
   void SetIntValue(const std::string& key, int value) const;
 
+  // Whether or not a value has been set for |key|.
+  bool HasValue(const std::string& key) const;
+
   scoped_refptr<base::SequencedWorkerPool> worker_pool() const {
     return worker_pool_;
   }