Create ChromeEarlGrey waitForWebViewContainingText.

ios/web/public/test/web_view_content_test_util.h

Index: ios/web/public/test/web_view_content_test_util.h
diff --git a/ios/web/public/test/web_view_content_test_util.h b/ios/web/public/test/web_view_content_test_util.h
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index 0000000000000000000000000000000000000000..9f877038d3ac0925185159afe4dce99e4a6da09a
--- /dev/null
+++ b/ios/web/public/test/web_view_content_test_util.h
@@ -0,0 +1,20 @@
+// Copyright 2017 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_PUBLIC_TEST_WEB_VIEW_CONTENT_TEST_UTIL_H_
+#define IOS_WEB_PUBLIC_TEST_WEB_VIEW_CONTENT_TEST_UTIL_H_
+
+#import "ios/web/public/web_state/web_state.h"
+
+namespace web {
+namespace test {
+
+// Returns true if there is a web view for |web_state| that contains |text|.
+// Otherwise, returns false.

[Eugene But (OOO till 7-30), 2017/04/21 18:49:21]

Do you want to mention anything about "timeout"?

[baxley, 2017/04/21 20:09:01]

Are you suggesting to say that this method doesn't timeout?

This method doesn't wait for a timeout. It waits for JS execution to complete,
but when it's done it simply returns the result. The callers (in ChromeEarlGrey
and ShellEarlGrey) do the waiting and talk about timeout.

[Eugene But (OOO till 7-30), 2017/04/21 21:37:46]

This method does "timeout". JS execution can "timeout", not sure if that's
useful to mention.

[baxley, 2017/04/21 22:41:58]

I don't consider it a timeout in the same sense to the user. These timeouts are
implementation details in making JS call synchronous. I know ExecuteJavaScript
uses a timeout in its implementation.

I feel like timeout has more meaning in the methods where the user is waiting
for a condition. This signifies that it didn't reach the condition within a
timeout, rather than reaching a state in which we know the condition will never
be met, or waiting indefinitely.

Anyway, I don't think we should say it in this comment, like we haven't for
other similar comments. It still returns true if it contains the text, and false
if it doesn't contain the text (regardless if there was an error or not). Any
objections?

[Eugene But (OOO till 7-30), 2017/04/21 22:46:15]

No objections.

+bool WebViewContainingText(web::WebState* web_state, const std::string& text);
+
+}  // namespace test
+}  // namespace web
+
+#endif  // IOS_WEB_PUBLIC_TEST_WEB_VIEW_CONTENT_TEST_UTIL_H_