[DevTools] Move DevToolsWindow testing code to a separate class.

chrome/browser/ui/cocoa/dev_tools_controller_browsertest.mm

Index: chrome/browser/ui/cocoa/dev_tools_controller_browsertest.mm
diff --git a/chrome/browser/ui/cocoa/dev_tools_controller_browsertest.mm b/chrome/browser/ui/cocoa/dev_tools_controller_browsertest.mm
index e22f829e675b969709127b3a7162bf3a4da1c0d0..516a7e74c29264007d55ec899638007ddc83c549 100644
--- a/chrome/browser/ui/cocoa/dev_tools_controller_browsertest.mm
+++ b/chrome/browser/ui/cocoa/dev_tools_controller_browsertest.mm
@@ -5,6 +5,7 @@
 #import "chrome/browser/ui/cocoa/dev_tools_controller.h"
 
 #include "chrome/browser/devtools/devtools_window.h"
+#include "chrome/browser/devtools/devtools_window_testing.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_list.h"
 #include "chrome/browser/ui/browser_window.h"
@@ -24,17 +25,11 @@ class DevToolsControllerTest : public InProcessBrowserTest {
  protected:
   void OpenDevToolsWindow() {
     devtools_window_ =
-        DevToolsWindow::OpenDevToolsWindowForTest(browser(), true);
+        DevToolsWindowTesting::OpenDevToolsWindowSync(browser(), true);
   }
 
   void CloseDevToolsWindow() {
-    content::WindowedNotificationObserver close_observer(
-        content::NOTIFICATION_WEB_CONTENTS_DESTROYED,
-        content::Source<content::WebContents>(
-            devtools_window_->web_contents_for_test()));
-    DevToolsWindow::ToggleDevToolsWindow(
-        browser(), DevToolsToggleAction::Toggle());
-    close_observer.Wait();
+    DevToolsWindowTesting::CloseDevToolsWindowSync(devtools_window_);
   }
 
   content::WebContents* web_contents() {