Web shell test to go back and forward.

ios/web/shell/test/utils/web_view_egutil.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/utils/web_view_egutil.h"
+
+#import <WebKit/WebKit.h>
+
+#import "base/test/ios/wait_util.h"
+#import "ios/web/shell/view_controller.h"
+#include "ios/web/shell/test/utils/eg_util.h"
+
+namespace {
+
+// Constant for UI wait loop.
+const NSTimeInterval kSpinDelaySeconds = 0.01;
+
+// Constant for timeout while waiting for web element.
+const NSTimeInterval kMaxTimeout = 4.0;
+
+// Script that returns document.body as a string.
+NSString* const kGetDocumentBodyJavaScript =
+    @"document.body ? document.body.textContent : null";
+}
+
+@implementation GREYMatchers (WebShellAdditions)
+
++ (id<GREYMatcher>)matcherForWebViewContainingText:(NSString*)text {
+  MatchesBlock matches = ^BOOL(UIView* view) {
+    if (![view isKindOfClass:[WKWebView class]]) {
+      return NO;
+    }
+
+    CRWWebController* webController = earl_grey_util::GetCurrentWebController();
+    DCHECK(webController);
+
+    __block id script = nil;
+    __block BOOL didSuceed = NO;
+    __block BOOL timeout = NO;
+    NSDate* deadline = [NSDate dateWithTimeIntervalSinceNow:kMaxTimeout];
+    script = ^(NSString* evaluationResult, NSError* error) {
+      if (![evaluationResult containsString:text]) {
+        if ([[NSDate date] compare:deadline] == NSOrderedDescending) {
+          timeout = YES;
+          return;
+        }
+        [webController evaluateJavaScript:kGetDocumentBodyJavaScript
+                      stringResultHandler:script];
+      } else {
+        didSuceed = YES;
+      }
+    };
+
+    [webController evaluateJavaScript:kGetDocumentBodyJavaScript
+                  stringResultHandler:script];
+    while (!didSuceed && !timeout) {
+      base::test::ios::SpinRunLoopWithMaxDelay(
+          base::TimeDelta::FromSecondsD(kSpinDelaySeconds));
+    }
+    return didSuceed;
+
+  };
+
+  DescribeToBlock describe = ^void(id<GREYDescription> description) {
+    [description
+        appendText:[NSString stringWithFormat:@"web view containing %@", text]];
+  };
+
+  base::scoped_nsobject<GREYElementMatcherBlock> matcherBlock(
+      [[[GREYElementMatcherBlock alloc] initWithMatchesBlock:matches
+                                            descriptionBlock:describe] retain]);
+  return matcherBlock;
+}
+
+@end
+
+#if !(GREY_DISABLE_SHORTHAND)
+
+id<GREYMatcher> shell_webViewContainingText(NSString* text) {
+  return [GREYMatchers matcherForWebViewContainingText:text];
+}
+
+#endif