MD History: add sign in promo in synced tabs when user isn't logged in

chrome/browser/resources/md_history/synced_device_manager.js

Index: chrome/browser/resources/md_history/synced_device_manager.js
diff --git a/chrome/browser/resources/md_history/synced_device_manager.js b/chrome/browser/resources/md_history/synced_device_manager.js
index ab273b3e73a71c7d4dddb73667f6e435bae428f2..92679068ca0971d7486bcbc92af01418ef12c1bb 100644
--- a/chrome/browser/resources/md_history/synced_device_manager.js
+++ b/chrome/browser/resources/md_history/synced_device_manager.js
@@ -36,6 +36,16 @@ Polymer({
     syncedDevices_: {
       type: Array,
       value: function() { return []; }
+    },
+
+    signInState_: {
+      type: Boolean,
+      value: loadTimeData.getBoolean('isUserSignedIn'),
+    },
+
+    fetchingSyncedTabs_: {
+      type: Boolean,
+      value: false,
     }
   },
 
@@ -81,6 +91,35 @@ Polymer({
     };
   },
 
+
+  onSignInTap_: function() {
+    chrome.send('SyncSetupShowSetupUI');
+    chrome.send('SyncSetupStartSignIn', [false]);
+  },
+
+  clearDisplayedSyncedDevices: function() {
+    this.syncedDevices_ = [];
+  },
+
+  /**
+   * Decide whether or not should display no synced tabs message.
+   * @param {boolean} signInState
+   * @param {number} syncedDevicesLength

[tsergeant, 2016/06/21 04:33:51]

Add an @return

[lshang, 2016/06/21 05:40:00]

Done.

+   */
+  showNoSyncedMessage: function(signInState, syncedDevicesLength) {
+    return signInState && syncedDevicesLength == 0;
+  },
+
+  /**
+   * Decide what message should be diaplayed when user is logged in and there is

[tsergeant, 2016/06/21 04:33:51]

Minor nit: typo in "displayed"

also, 

"there are no synced tabs"

[lshang, 2016/06/21 05:40:00]

Done.

+   * no synced tabs.
+   * @param {boolean} fetchingSyncedTabs

[tsergeant, 2016/06/21 04:33:51]

Add an @return as well

[lshang, 2016/06/21 05:40:00]

Done.

+   */
+  noSyncedTabsMessage: function(fetchingSyncedTabs) {
+    return loadTimeData.getString(
+        fetchingSyncedTabs ? 'loading' : 'noSyncedResults');
+  },
+
   /**
    * Replaces the currently displayed synced tabs with |sessionList|. It is
    * common for only a single session within the list to have changed, We try to
@@ -90,8 +129,10 @@ Polymer({
    * @param {?Array<!ForeignSession>} sessionList
    */
   updateSyncedDevices: function(sessionList) {
-    if (!sessionList)
+    if (!sessionList) {
+      this.fetchingSyncedTabs_ = false;

[tsergeant, 2016/06/21 04:33:51]

Just put this once at the very start of the method. Then you'll be able to
remove the duplicate line below.

[lshang, 2016/06/21 05:40:00]

Done.

       return;
+    }
 
     // First, update any existing devices that have changed.
     var updateCount = Math.min(sessionList.length, this.syncedDevices_.length);
@@ -108,10 +149,35 @@ Polymer({
     for (var i = updateCount; i < sessionList.length; i++) {
       this.push('syncedDevices_', this.createInternalDevice_(sessionList[i]));
     }
+
+    this.fetchingSyncedTabs_ = false;
+  },
+
+  /**
+   * 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 is no synced tabs.
+   * @param {boolean} isUserSignedIn
+   */
+  updateSignInState: function(isUserSignedIn) {
+    // If user's sign in state didn't change, then don't change message or
+    // update UI.
+    if (this.signInState_ == isUserSignedIn)
+      return;
+    this.signInState_ = isUserSignedIn;
+
+    // User signed out, clear synced device list and show the sign in promo.
+    if (!isUserSignedIn) {
+      this.clearDisplayedSyncedDevices();
+    } else {
+      // User signed in, show the loading message when querying for synced
+      // devices.
+      this.fetchingSyncedTabs_ = true;
+    }
   },
 
   searchTermChanged: function(searchedTerm) {
-    this.syncedDevices_ = [];
+    this.clearDisplayedSyncedDevices();
     this.updateSyncedDevices(this.sessionList);
   }
 });