alternate ntp: implement Show/HideBars API to reduce jank when showing/hiding bars

chrome/renderer/resources/extensions/searchbox_api.js

Index: chrome/renderer/resources/extensions/searchbox_api.js
diff --git a/chrome/renderer/resources/extensions/searchbox_api.js b/chrome/renderer/resources/extensions/searchbox_api.js
index d5d58afbbfd0f7cd9f5855ec06fc09226e307b5c..1a2d01a705e1ac25204105502da42de872e9f93b 100644
--- a/chrome/renderer/resources/extensions/searchbox_api.js
+++ b/chrome/renderer/resources/extensions/searchbox_api.js
@@ -102,6 +102,8 @@ if (!chrome.embeddedSearch) {
       native function FocusOmnibox();
       native function StartCapturingKeyStrokes();
       native function StopCapturingKeyStrokes();
+      native function ShowBars();
+      native function HideBars();
 
       function SafeWrapSuggestion(restrictedText) {
         return SafeWrap(restrictedText, window.innerWidth - 155, 22);
@@ -266,6 +268,12 @@ if (!chrome.embeddedSearch) {
       this.stopCapturingKeyStrokes = function() {
         StopCapturingKeyStrokes();
       };
+      this.showBars = function() {
+        ShowBars();
+      };
+      this.hideBars = function() {
+        HideBars();
+      };
       this.onchange = null;
       this.onsubmit = null;
       this.oncancel = null;
@@ -275,6 +283,7 @@ if (!chrome.embeddedSearch) {
       this.oncontextchange = null;
       this.onmarginchange = null;
       this.onnativesuggestions = null;
+      this.onbarshidden = null;
 
       // DEPRECATED. These methods are from the legacy searchbox API.
       // TODO(jered): Delete these.