Bug 1364768: Part 2 - Add AsyncShutdown finalizer support to DeferredSave. r=rhelmer

MozReview-Commit-ID: LAvOErU1YB8

--HG--
extra : rebase_source : a64786b0a44ba70f500c7e3686c89023d643eb76

toolkit/mozapps/extensions/DeferredSave.jsm

@@ -43,6 +43,11 @@ parentLogger.addAppender(new Log.DumpAppender(formatter));
 // at DEBUG and higher should go to JS console and standard error.
 Cu.import("resource://gre/modules/Services.jsm");
 
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "AsyncShutdown",
+                                  "resource://gre/modules/AsyncShutdown.jsm");
+
 const PREF_LOGGING_ENABLED = "extensions.logging.enabled";
 const NS_PREFBRANCH_PREFCHANGE_TOPIC_ID = "nsPref:changed";
 
@@ -83,21 +88,30 @@ PrefObserver.init();
  * fulfilled by a single write.
  *
  * @constructor
- * @param aPath
+ * @param {string} aPath
  *        String representing the full path of the file where the data
  *        is to be written.
- * @param aDataProvider
+ * @param {function} aDataProvider
  *        Callback function that takes no argument and returns the data to
  *        be written. If aDataProvider returns an ArrayBufferView, the
  *        bytes it contains are written to the file as is.
  *        If aDataProvider returns a String the data are UTF-8 encoded
  *        and then written to the file.
- * @param [optional] aDelay
+ * @param {object | integer} [aOptions]
  *        The delay in milliseconds between the first saveChanges() call
  *        that marks the data as needing to be saved, and when the DeferredSave
  *        begins writing the data to disk. Default 50 milliseconds.
+ *
+ *        Or, an options object containing:
+ *         - delay: A delay in milliseconds.
+ *         - finalizeAt: An AsyncShutdown blocker during which to
+ *           finalize any pending writes.
  */
-this.DeferredSave = function(aPath, aDataProvider, aDelay) {
+this.DeferredSave = function(aPath, aDataProvider, aOptions = {}) {
+  if (typeof aOptions == "number") {
+    aOptions = {delay: aOptions};
+  }
+
   // Create a new logger (child of 'DeferredSave' logger)
   // for use by this particular instance of DeferredSave object
   let leafName = OS.Path.basename(aPath);
@@ -141,10 +155,15 @@ this.DeferredSave = function(aPath, aDataProvider, aDelay) {
   // Error returned by the most recent write (if any)
   this._lastError = null;
 
-  if (aDelay && (aDelay > 0))
-    this._delay = aDelay;
+  if (aOptions.delay && (aOptions.delay > 0))
+    this._delay = aOptions.delay;
   else
     this._delay = DEFAULT_SAVE_DELAY_MS;
+
+  this._finalizeAt = aOptions.finalizeAt || AsyncShutdown.profileBeforeChange;
+  this._finalize = this._finalize.bind(this);
+  this._finalizeAt.addBlocker(`DeferredSave: writing data to ${aPath}`,
+                              this._finalize);
 }
 
 this.DeferredSave.prototype = {
@@ -156,6 +175,10 @@ this.DeferredSave.prototype = {
     return this._lastError;
   },
 
+  get path() {
+    return this._path;
+  },
+
   // Start the pending timer if data is dirty
   _startTimer() {
     if (!this._pending) {
@@ -263,5 +286,10 @@ this.DeferredSave.prototype = {
     }
 
     return this._writing;
-  }
+  },
+
+  _finalize() {
+    return this.flush().catch(Cu.reportError);
+  },
+
 };