MD History: Hide sign in guide in guest mode

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 8df8973d7b22dac9e45f4cd467e8b5d53614a5c9..be5ba0d795b624850a211ef4c675816b0eae78fb 100644
--- a/chrome/browser/resources/md_history/synced_device_manager.js
+++ b/chrome/browser/resources/md_history/synced_device_manager.js
@@ -45,6 +45,12 @@ Polymer({
     },
 
     /** @private */
+    guestSession_: {
+      type: Boolean,
+      value: loadTimeData.getBoolean('isGuestSession'),
+    },
+
+    /** @private */
     fetchingSyncedTabs_: {
       type: Boolean,
       value: false,
@@ -108,13 +114,29 @@ Polymer({
    * Decide whether or not should display no synced tabs message.
    * @param {boolean} signInState
    * @param {number} syncedDevicesLength
+   * @param {boolean} guestSession
    * @return {boolean}
    */
-  showNoSyncedMessage: function(signInState, syncedDevicesLength) {
+  showNoSyncedMessage: function(
+      signInState, syncedDevicesLength, guestSession) {
+    if (guestSession)
+      return true;
+
     return signInState && syncedDevicesLength == 0;
   },
 
   /**
+   * Shows the signin guide when the user is not signed in and not in a guest
+   * session.
+   * @param {boolean} signInState
+   * @param {boolean} guestSession
+   * @return {boolean}
+   */
+  showSignInGuide: function(signInState, guestSession) {
+    return !signInState && !guestSession;
+  },
+
+  /**
    * Decide what message should be displayed when user is logged in and there
    * are no synced tabs.
    * @param {boolean} fetchingSyncedTabs