[Sync] Removing complexity around PROXY_TABS now that empty sessions are provided when disabled.

chrome/browser/resources/md_history/synced_device_manager.js

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @typedef {{device: string,
  *           lastUpdateTime: string,
  *           opened: boolean,
  *           separatorIndexes: !Array<number>,
  *           timestamp: number,
@@ skipping 249 matching lines @@
     sessionList.forEach(function(session) {
       var device = this.createInternalDevice_(session);
       if (device.tabs.length != 0)
         devices.push(device);
     }.bind(this));
 
     this.syncedDevices_ = devices;
   },
 
   /**
-   * End fetching synced tabs when sync is disabled.
-   */
-  tabSyncDisabled: function() {
-    this.fetchingSyncedTabs_ = false;
-    this.clearDisplayedSyncedDevices_();
-  },
-
-  /**
    * Get called when user's sign in state changes, this will affect UI of synced
    * tabs page. Sign in promo gets displayed when user is signed out, and
    * different messages are shown when there are no synced tabs.
    */
   signInStateChanged_: function() {
     this.fire('history-view-changed');
 
     // User signed out, clear synced device list and show the sign in promo.
     if (!this.signInState) {
       this.clearDisplayedSyncedDevices_();
       return;
     }
     // User signed in, show the loading message when querying for synced
     // devices.
     this.fetchingSyncedTabs_ = true;
   },
 
   searchTermChanged: function(searchTerm) {
     this.clearDisplayedSyncedDevices_();
     this.updateSyncedDevices(this.sessionList);
   }
 });