[ios] Implemented -[ShellEarlGrey loadURL:].

ios/web/shell/test/earl_grey/shell_earl_grey.mm

+// Copyright 2016 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/shell/test/earl_grey/shell_earl_grey.h"
+
+#import <EarlGrey/EarlGrey.h>
+
+#import "ios/web/public/test/earl_grey/js_test_util.h"
+#include "ios/web/shell/test/app/navigation_test_util.h"
+#import "ios/web/shell/test/app/web_shell_test_util.h"
+
+namespace {
+const NSTimeInterval kWaitForPageLoadTimeout = 10.0;
+}  // namespace
+
+@implementation ShellEarlGrey
+
++ (void)loadURL:(const GURL&)URL {
+  web::shell_test_util::LoadUrl(URL);
+
+  // Make sure that the page started loading.
+  GREYAssert(web::shell_test_util::IsLoading(), @"Page did not start loading.");
+
+  GREYCondition* condition =
+      [GREYCondition conditionWithName:@"Wait for page to complete loading."
+                                 block:^BOOL {
+                                   return !web::shell_test_util::IsLoading();
+                                 }];
+  GREYAssert([condition waitWithTimeout:kWaitForPageLoadTimeout],
+             @"Page did not complete loading.");
+
+  web::WebState* webState = web::shell_test_util::GetCurrentWebState();
+  if (webState->ContentIsHTML())
+    web::WaitUntilWindowIdInjected(webState);
+}
+
+@end