Handle extension webrequest API on the IO thread. This speeds up blocking event

chrome/browser/ui/panels/panel_browser_view_browsertest.cc

Index: chrome/browser/ui/panels/panel_browser_view_browsertest.cc
diff --git a/chrome/browser/ui/panels/panel_browser_view_browsertest.cc b/chrome/browser/ui/panels/panel_browser_view_browsertest.cc
index a35620fedfd3760c0bbaf7b27a3b7356ae184f61..863f99204499f53121c38ef577d28b3447c29276 100644
--- a/chrome/browser/ui/panels/panel_browser_view_browsertest.cc
+++ b/chrome/browser/ui/panels/panel_browser_view_browsertest.cc
@@ -215,13 +215,9 @@ class PanelBrowserViewTest : public InProcessBrowserTest {
         &error);
     ASSERT_TRUE(extension.get());
     EXPECT_STREQ("", error.c_str());
-    browser()->GetProfile()->GetExtensionService()->AddExtension(
+    browser()->GetProfile()->GetExtensionService()->OnLoadSingleExtension(
         extension.get());
 
-    // Makes sure that async task ExtensionPrefs::OnExtensionInstalled gets a
-    // chance to be procesed.
-    MessageLoop::current()->RunAllPending();
-
     // Creates a panel with the app name that comes from the extension ID.
     PanelBrowserView* browser_view = CreatePanelBrowserView(
         web_app::GenerateApplicationNameFromExtensionId(extension->id()));