Don't wake up to check messages if not registered

This chrome alarm business is in place to help us wake up and check for
messages when running in the background. Without it, chrome will suspend
our app after a short period of inactivity. Upon waking, if the app
discovers it is not linked, it prompts you to link it. However, if
you've declined registration (i.e., because you already maxed out your
linked device limit, but chrome auto-added the app to another machine),
we should just wait until explicitly launched again.

Fixes #519

// FREEBIE

js/background.js

@@ -23,12 +23,6 @@
             }
         });
     }
-    if (chrome && chrome.alarms) {
-        chrome.alarms.onAlarm.addListener(function() {
-            // nothing to do.
-        });
-        chrome.alarms.create('awake', {periodInMinutes: 1});
-    }
 
     // Close and reopen existing windows
     var open = false;
@@ -74,10 +68,12 @@
         setUnreadCount(storage.get("unreadCount", 0));
 
         if (textsecure.registration.isDone()) {
+            extension.keepAwake();
             init();
         }
 
         extension.on('registration_done', function() {
+            extension.keepAwake();
             init(true);
         });
 

js/chromium.js

@@ -231,6 +231,15 @@
         }
     };
 
+    extension.keepAwake = function() {
+        if (chrome && chrome.alarms) {
+            chrome.alarms.onAlarm.addListener(function() {
+                // nothing to do.
+            });
+            chrome.alarms.create('awake', {periodInMinutes: 1});
+        }
+    };
+
     if (chrome.runtime.onInstalled) {
         chrome.runtime.onInstalled.addListener(function(options) {
             if (options.reason === 'install') {