[ios] Implemented -[ShellEarlGrey loadURL:].

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

+// 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.
+
+#ifndef IOS_WEB_SHELL_TEST_EARL_GREY_SHELL_EARL_GREY_H_
+#define IOS_WEB_SHELL_TEST_EARL_GREY_SHELL_EARL_GREY_H_
+
+#import <Foundation/Foundation.h>
+
+#include "url/gurl.h"
+
+// Test methods that perform actions on Web Shell. These methods may read or
+// alter Web Shell's internal state programmatically or via the UI, but in both
+// cases will properly synchronize the UI for Earl Grey tests.
+@interface ShellEarlGrey : NSObject
+
+// Loads |URL| in the current WebState with transition of type
+// ui::PAGE_TRANSITION_TYPED, and waits for the page to complete loading, or
+// a timeout.
++ (void)loadURL:(const GURL&)URL;
+
+@end
+
+#endif  // IOS_WEB_SHELL_TEST_EARL_GREY_SHELL_EARL_GREY_H_