MD History: Add icon in top right of page when showing synced results

chrome/browser/resources/md_history/history_toolbar.js

Index: chrome/browser/resources/md_history/history_toolbar.js
diff --git a/chrome/browser/resources/md_history/history_toolbar.js b/chrome/browser/resources/md_history/history_toolbar.js
index d346317e913f5fc1cb10b098c0b94610f010e0a4..c3cc51fd65b7f68a3c95e030d3a6b5242003783e 100644
--- a/chrome/browser/resources/md_history/history_toolbar.js
+++ b/chrome/browser/resources/md_history/history_toolbar.js
@@ -42,6 +42,8 @@ Polymer({
       reflectToAttribute: true,
     },
 
+    showSyncNotice: Boolean,
+
     // Whether domain-grouped history is enabled.
     isGroupedMode: {
       type: Boolean,
@@ -96,6 +98,17 @@ Polymer({
     this.searchTerm = /** @type {string} */ (event.detail);
   },
 
+  /** @private */
+  onInfoButtonTap_: function() {
+    this.$.syncNotice.get().then(function(dropdown) {
+      dropdown.positionTarget = this.$$('#info-button-icon');
+      // It is possible for this listener to trigger while the dialog is
+      // closing. Ensure the dialog is fully closed before reopening it.
+      if (dropdown.style.display == 'none')
+        dropdown.open();
+    }.bind(this));
+  },
+
   onClearSelectionTap_: function() {
     this.fire('unselect-all');
   },