Instant: Use only one hidden WebContents per profile.

chrome/renderer/resources/renderer_resources.grd

Index: chrome/renderer/resources/renderer_resources.grd
diff --git a/chrome/renderer/resources/renderer_resources.grd b/chrome/renderer/resources/renderer_resources.grd
index 8a95160095a76c92e3bc03a39110787fd82d8ab5..c1ad4348350d307028ded238b9d2c44e94b36808 100644
--- a/chrome/renderer/resources/renderer_resources.grd
+++ b/chrome/renderer/resources/renderer_resources.grd
@@ -24,6 +24,7 @@ without changes to the corresponding grd file. fb9 -->
       <include name="IDR_CLICK_TO_PLAY_PLUGIN_HTML" file="click_to_play_plugin.html" flattenhtml="true" type="BINDATA" />
       <include name="IDR_CONTENT_WATCHER_JS" file="extensions\content_watcher.js" type="BINDATA" />
       <include name="IDR_DISABLED_PLUGIN_HTML" file="disabled_plugin.html" flattenhtml="true" type="BINDATA" />
+      <include name="IDR_EMBEDDED_SEARCHBOX_API" file="extensions\embedded_searchbox_api.js" type="BINDATA" />
       <include name="IDR_ERROR_APP_HTML" file="error_app.html" flattenhtml="true" type="BINDATA" />
       <include name="IDR_EVENT_BINDINGS_JS" file="extensions\event.js" type="BINDATA" />
       <include name="IDR_GREASEMONKEY_API_JS" file="extensions\greasemonkey_api.js" type="BINDATA" />