Convert Google Now's use of chrome.local.storage.get to use Promises

chrome/browser/resources/google_now/utility.js

Index: chrome/browser/resources/google_now/utility.js
diff --git a/chrome/browser/resources/google_now/utility.js b/chrome/browser/resources/google_now/utility.js
index f2236209fc498ffa15c0b2cc10c89d254e5a8c84..2946dc0dfa8e3809b2b57c2879ce0b66b9eb016f 100644
--- a/chrome/browser/resources/google_now/utility.js
+++ b/chrome/browser/resources/google_now/utility.js
@@ -323,7 +323,7 @@ var wrapper = (function() {
           wrapperPluginInstance.prologue();
 
         // Call the original callback.
-        callback.apply(null, arguments);
+        var returnValue = callback.apply(null, arguments);
 
         if (wrapperPluginInstance)
           wrapperPluginInstance.epilogue();
@@ -331,6 +331,8 @@ var wrapper = (function() {
         verify(isInWrappedCallback,
                'Instrumented callback is not instrumented upon exit');
         isInWrappedCallback = false;
+
+        return returnValue;
       } catch (error) {
         reportError(error);
       }
@@ -434,6 +436,7 @@ wrapper.instrumentChromeApiFunction('alarms.onAlarm.addListener', 0);
 wrapper.instrumentChromeApiFunction('identity.getAuthToken', 1);
 wrapper.instrumentChromeApiFunction('identity.onSignInChanged.addListener', 0);
 wrapper.instrumentChromeApiFunction('identity.removeCachedAuthToken', 1);
+wrapper.instrumentChromeApiFunction('storage.local.get', 1);
 wrapper.instrumentChromeApiFunction('webstorePrivate.getBrowserLogin', 0);
 
 /**
@@ -458,6 +461,47 @@ Promise.prototype.catch = function() {
   }
 }();
 
+
+/*

[skare_, 2014/02/20 00:17:12]

nit: /* -> /** and in :472 
(sorry!)

[robliao, 2014/02/21 21:25:45]

Done.

+ * Disallow promise rejection.
+ * @type {boolean}
+ * @const
+ */
+var NO_PROMISE_REJECTION = false;

[skare_, 2014/02/20 00:17:12]

(no action required)
this works; could make an @enum {boolean} too

[robliao, 2014/02/21 21:25:45]

Done.

+
+/*
+ * Allow promise rejection.
+ * @type {boolean}
+ * @const
+ */
+var ALLOW_PROMISE_REJECTION = true;
+
+/**
+ * Provides the promise equivalent of instrumented.chrome.local.get.

[skare_, 2014/02/20 00:17:12]

instrumented.chrome.storage.local?

[robliao, 2014/02/21 21:25:45]

Done.

+ * @param {Object} defaultStorageObject Default storage object to fill.
+ * @param {boolean} opt_allowPromiseRejection If ALLOW_PROMISE_REJECTION,
+ *     allows promise rejection on errors, otherwise the default storage
+ *     object is resolved.
+ * @return {Promise} A promise that fills the default storage object. On

[skare_, 2014/02/20 00:17:12]

just as a first-read opinion, "fills" is slightly confusing but that might just
be me. It's basically "get from" or "read from" right? (those aren't great
suggestions because they might make a couple things wordy elsewhere)

[robliao, 2014/02/21 21:25:45]

I'm open to other suggestions.

I chose fill because we are filling the object in, replacing default values with
the stored values.

get didn't work because we return the default object if anything failed.
On 2014/02/20 00:17:12, Travis Skare wrote:

+ *     failure, if promise rejection is a allowed, the promise is rejected,

[skare_, 2014/02/20 00:17:12]

nit: is a allowed -> is allowed

[robliao, 2014/02/21 21:25:45]

Done.

+ *     otherwise it is resolved to the default storage object.
+ */
+function fillFromChromeLocalStorage(
+    defaultStorageObject,
+    opt_allowPromiseRejection) {
+  return new Promise(function(resolve, reject) {
+    instrumented.storage.local.get(defaultStorageObject, function(items) {
+      if (items) {
+        resolve(items);
+      } else if (opt_allowPromiseRejection === ALLOW_PROMISE_REJECTION) {
+        reject();
+      } else {
+        resolve(defaultStorageObject);
+      }
+    });
+  });
+}
+
 /**
  * Builds the object to manage tasks (mutually exclusive chains of events).
  * @param {function(string, string): boolean} areConflicting Function that
@@ -699,11 +743,9 @@ function buildAttemptManager(
    *     the planning is done.
    */
   function planForNext(callback) {
-    instrumented.storage.local.get(currentDelayStorageKey, function(items) {
-      if (!items) {
-        items = {};
-        items[currentDelayStorageKey] = maximumDelaySeconds;
-      }
+    var request = {};
+    request[currentDelayStorageKey] = maximumDelaySeconds;
+    fillFromChromeLocalStorage(request).then(function(items) {
       console.log('planForNext-get-storage ' + JSON.stringify(items));
       scheduleNextAttempt(items[currentDelayStorageKey]);
       callback();
@@ -797,17 +839,17 @@ function buildAuthenticationManager() {
    */
   function checkAndNotifyListeners() {
     isSignedIn().then(function(signedIn) {
-      instrumented.storage.local.get('lastSignedInState', function(items) {
-        items = items || {};
-        if (items.lastSignedInState != signedIn) {
-          chrome.storage.local.set(
-              {lastSignedInState: signedIn});
-          listeners.forEach(function(callback) {
-            callback();
-          });
-        }
+      fillFromChromeLocalStorage({lastSignedInState: undefined})
+          .then(function(items) {
+            if (items.lastSignedInState != signedIn) {
+              chrome.storage.local.set(
+                  {lastSignedInState: signedIn});
+              listeners.forEach(function(callback) {
+                callback();
+              });
+            }
+        });
       });
-    });
   }
 
   instrumented.identity.onSignInChanged.addListener(function() {