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 24b2bc142cb9320382c8276949655c9a25b22921..736e7d7bfc1e600a045da45cfe818a6ed239fcaa 100644
--- a/chrome/renderer/resources/extensions/searchbox_api.js
+++ b/chrome/renderer/resources/extensions/searchbox_api.js
@@ -105,6 +105,8 @@ if (!chrome.embeddedSearch) {
       native function StartCapturingKeyStrokes();
       native function StopCapturingKeyStrokes();
       native function NavigateSearchBox();
+      native function ShowBars();
+      native function HideBars();
 
       function SafeWrapSuggestion(restrictedText) {
         return SafeWrap(restrictedText, window.innerWidth - 155, 22);
@@ -272,6 +274,12 @@ if (!chrome.embeddedSearch) {
       this.navigateContentWindow = function(destination, disposition) {
         NavigateSearchBox(destination, disposition);
       }
+      this.showBars = function() {
+        ShowBars();
+      };
+      this.hideBars = function() {
+        HideBars();
+      };
       this.onchange = null;
       this.onsubmit = null;
       this.oncancel = null;
@@ -281,6 +289,7 @@ 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.