Refactor wait_util so it isn't coupled to EarlGrey.

ios/web/shell/test/earl_grey/shell_matchers.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_matchers.h"
 
 #import "base/mac/foundation_util.h"
 #include "base/strings/sys_string_conversions.h"
 #import "ios/testing/earl_grey/matchers.h"
-#include "ios/testing/earl_grey/wait_util.h"
+#include "ios/testing/wait_util.h"
 #import "ios/web/public/web_state/web_state.h"
 #import "ios/web/public/test/earl_grey/web_view_matchers.h"
 #import "ios/web/shell/test/app/web_shell_test_util.h"
 #import "ios/web/shell/view_controller.h"
 
 namespace web {
 
 id<GREYMatcher> webViewContainingText(const std::string& text) {
   WebState* web_state = shell_test_util::GetCurrentWebState();
   return webViewContainingText(std::move(text), web_state);
@@ skipping 15 matching lines @@
 id<GREYMatcher> addressFieldText(std::string text) {
   MatchesBlock matches = ^BOOL(UIView* view) {
     if (![view isKindOfClass:[UITextField class]]) {
       return NO;
     }
     if (![[view accessibilityLabel]
             isEqualToString:kWebShellAddressFieldAccessibilityLabel]) {
       return NO;
     }
     UITextField* text_field = base::mac::ObjCCastStrict<UITextField>(view);
-    testing::WaitUntilCondition(testing::kWaitForUIElementTimeout, ^bool() {
-      return [text_field.text isEqualToString:base::SysUTF8ToNSString(text)];
-    });
+    NSString* errorMessage = [NSString
+        stringWithFormat:
+            @"Address field text did not match. expected: %@, actual: %@",
+            base::SysUTF8ToNSString(text), text_field.text];
+    GREYAssert(testing::WaitUntilConditionOrTimeout(
+                   testing::kWaitForUIElementTimeout,
+                   ^() {
+                     return [text_field.text
+                         isEqualToString:base::SysUTF8ToNSString(text)];
+                   }),
+               errorMessage);
     return YES;
   };
 
   DescribeToBlock describe = ^(id<GREYDescription> description) {
     [description appendText:@"address field containing "];
     [description appendText:base::SysUTF8ToNSString(text)];
   };
 
   return [[[GREYElementMatcherBlock alloc] initWithMatchesBlock:matches
                                                descriptionBlock:describe]
       autorelease];
 }
 
 id<GREYMatcher> backButton() {
   return grey_accessibilityLabel(kWebShellBackButtonAccessibilityLabel);
 }
 
 id<GREYMatcher> forwardButton() {
   return grey_accessibilityLabel(kWebShellForwardButtonAccessibilityLabel);
 }
 
 id<GREYMatcher> addressField() {
   return grey_accessibilityLabel(kWebShellAddressFieldAccessibilityLabel);
 }
 
 }  // namespace web