[ios] Implemented -[ShellEarlGrey loadURL:].

ios/web/public/test/earl_grey/js_test_util.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/public/test/earl_grey/js_test_util.h"
+
+#import <EarlGrey/EarlGrey.h>
+#import <WebKit/WebKit.h>
+
+#include "base/timer/elapsed_timer.h"
+#import "ios/testing/earl_grey/wait_util.h"
+#import "ios/web/public/web_state/js/crw_js_injection_receiver.h"
+
+namespace web {
+
+void WaitUntilWindowIdInjected(WebState* web_state) {
+  bool is_window_id_injected = false;
+  bool is_timeout = false;
+  bool is_unrecoverable_error = false;
+
+  base::ElapsedTimer timer;
+  base::TimeDelta timeout =
+      base::TimeDelta::FromSeconds(testing::kWaitForJSCompletionTimeout);
+
+  // Keep polling until either the JavaScript execution returns with expected
+  // value (indicating that Window ID is set), the timeout occurs, or an
+  // unrecoverable error occurs.
+  while (!is_window_id_injected && !is_timeout && !is_unrecoverable_error) {
+    NSError* error = nil;
+    id result = ExecuteJavaScript(web_state, @"0", &error);
+    if (error) {
+      is_unrecoverable_error = ![error.domain isEqual:WKErrorDomain] ||
+                               error.code != WKErrorJavaScriptExceptionOccurred;
+    } else {
+      is_window_id_injected = [result isEqual:@0];
+    }
+    is_timeout = timeout < timer.Elapsed();
+  }
+  GREYAssertFalse(is_timeout, @"windowID injection timed out");
+  GREYAssertFalse(is_unrecoverable_error, @"script execution error");
+}
+
+id ExecuteJavaScript(WebState* web_state,
+                     NSString* javascript,
+                     NSError** out_error) {
+  __block BOOL did_complete = NO;
+  __block id result = nil;
+  CRWJSInjectionReceiver* receiver = web_state->GetJSInjectionReceiver();
+  [receiver executeJavaScript:javascript
+            completionHandler:^(id value, NSError* error) {
+              did_complete = YES;
+              result = [value copy];
+              if (out_error)
+                *out_error = [error copy];
+            }];
+
+  // Wait for completion.
+  GREYCondition* condition = [GREYCondition
+      conditionWithName:@"Wait for JavaScript execution to complete."
+                  block:^{
+                    return did_complete;
+                  }];
+  GREYAssert([condition waitWithTimeout:testing::kWaitForJSCompletionTimeout],
+             @"Script execution timed out");
+
+  if (out_error)
+    [*out_error autorelease];
+  return [result autorelease];
+}
+
+}  // namespace web