[ios] Cleaned up UIWebView workarounds from window_id.js.

ios/web/web_state/js/crw_js_window_id_manager_unittest.mm

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/web/web_state/js/crw_js_window_id_manager.h"
 
 #import <WebKit/WebKit.h>
 
 #import "ios/web/public/test/js_test_util.h"
+#import "ios/web/web_state/js/page_script_util.h"
 #import "testing/gtest_mac.h"
 
 namespace web {
 
 // Tests that window ID injection by a second manager results in a different
 // window ID.
 TEST(JSWindowIDManagerTest, WindowIDDifferentManager) {
   // Inject the first manager.
   WKWebView* web_view = [[[WKWebView alloc] init] autorelease];
-  EvaluateJavaScript(web_view, @"window.__gCrWeb = {};");
+  EvaluateJavaScript(web_view, GetEarlyPageScript());
 
   CRWJSWindowIDManager* manager =
       [[[CRWJSWindowIDManager alloc] initWithWebView:web_view] autorelease];
   [manager inject];
   EXPECT_NSEQ([manager windowID],
               EvaluateJavaScript(web_view, @"window.__gCrWeb.windowId"));
 
   // Inject the second manager.
   WKWebView* web_view2 = [[[WKWebView alloc] init] autorelease];
-  EvaluateJavaScript(web_view2, @"window.__gCrWeb = {};");
+  EvaluateJavaScript(web_view2, GetEarlyPageScript());
 
   CRWJSWindowIDManager* manager2 =
       [[[CRWJSWindowIDManager alloc] initWithWebView:web_view2] autorelease];
   [manager2 inject];
   EXPECT_NSEQ([manager2 windowID],
               EvaluateJavaScript(web_view2, @"window.__gCrWeb.windowId"));
 
   // Window IDs must be different.
   EXPECT_NSNE([manager windowID], [manager2 windowID]);
 }
 
 // Tests that injecting multiple times creates a new window ID.
 TEST(JSWindowIDManagerTest, MultipleInjections) {
   WKWebView* web_view = [[[WKWebView alloc] init] autorelease];
-  EvaluateJavaScript(web_view, @"window.__gCrWeb = {};");
+  EvaluateJavaScript(web_view, GetEarlyPageScript());
 
   // First injection.
   CRWJSWindowIDManager* manager =
       [[[CRWJSWindowIDManager alloc] initWithWebView:web_view] autorelease];
   [manager inject];
   NSString* windowID = [manager windowID];
   EXPECT_NSEQ(windowID,
               EvaluateJavaScript(web_view, @"window.__gCrWeb.windowId"));
 
   // Second injection.
   [manager inject];
   EXPECT_NSEQ([manager windowID],
               EvaluateJavaScript(web_view, @"window.__gCrWeb.windowId"));
 
   EXPECT_NSNE(windowID, [manager windowID]);
 }
 
 // Tests that injection will retry if |window.__gCrWeb| is not present.
 TEST(JSWindowIDManagerTest, InjectionRetry) {
   WKWebView* web_view = [[[WKWebView alloc] init] autorelease];
 
   CRWJSWindowIDManager* manager =
       [[[CRWJSWindowIDManager alloc] initWithWebView:web_view] autorelease];
   [manager inject];
   EXPECT_TRUE([manager windowID]);
   EXPECT_FALSE(EvaluateJavaScript(web_view, @"window.__gCrWeb"));
 
   // Now inject window.__gCrWeb and check if window ID injection retried.
-  EvaluateJavaScript(web_view, @"window.__gCrWeb = {};");
+  EvaluateJavaScript(web_view, GetEarlyPageScript());
   EXPECT_NSEQ([manager windowID],
               EvaluateJavaScript(web_view, @"window.__gCrWeb.windowId"));
 }
 
 }  // namespace web