detect preferences errors

chrome/browser/pref_service.h

Index: chrome/browser/pref_service.h
diff --git a/chrome/browser/pref_service.h b/chrome/browser/pref_service.h
index 85dd42ca8f7858ef2e18d44814ea8e9bc49b56bb..7a79286ee994fdacd919490116a611203cceb447 100644
--- a/chrome/browser/pref_service.h
+++ b/chrome/browser/pref_service.h
@@ -184,7 +184,23 @@ class PrefService : public NonThreadSafe,
   // ImportantFileWriter::DataSerializer
   virtual bool SerializeData(std::string* output);
 
+  bool read_only() const { return read_only_; }
+
  private:
+  // Unique integer code for each type of error so we can report them
+  // distinctly in a histogram.
+  // NOTE: Don't change the order here as it will change the server's meaning
+  // of the histogram.
+  enum PrefReadError {
+    PREF_READ_ERROR_NONE = 0,
+    PREF_READ_ERROR_JSON_PARSE,
+    PREF_READ_ERROR_JSON_TYPE,
+    PREF_READ_ERROR_ACCESS_DENIED,
+    PREF_READ_ERROR_FILE_OTHER,
+    PREF_READ_ERROR_FILE_LOCKED,
+    PREF_READ_ERROR_NO_FILE,
+  };
+
   // Add a preference to the PreferenceMap.  If the pref already exists, return
   // false.  This method takes ownership of |pref|.
   void RegisterPreference(Preference* pref);
@@ -201,6 +217,13 @@ class PrefService : public NonThreadSafe,
   void FireObserversIfChanged(const wchar_t* pref_name,
                               const Value* old_value);
 
+  // Load from disk.  Returns a non-zero error code on failure.
+  PrefReadError LoadPersistentPrefs();
+
+  // Load preferences from disk, attempting to diagnose and handle errors.
+  // This should only be called from the constructor.
+  void InitFromDisk();
+
   scoped_ptr<DictionaryValue> persistent_;
 
   // Helper for safe writing pref data.
@@ -216,6 +239,11 @@ class PrefService : public NonThreadSafe,
       PrefObserverMap;
   PrefObserverMap pref_observers_;
 
+  // Whether the service is in a pseudo-read-only mode where changes are not
+  // actually persisted to disk.  This happens in some cases when there are
+  // read errors during startup.
+  bool read_only_;
+
   DISALLOW_COPY_AND_ASSIGN(PrefService);
 };