Refactor wait_util so it isn't coupled to EarlGrey.

ios/testing/wait_util.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_TESTING_EARL_GREY_WAIT_UTIL_H_
-#define IOS_TESTING_EARL_GREY_WAIT_UTIL_H_
+#ifndef IOS_TESTING_WAIT_UTIL_H_
+#define IOS_TESTING_WAIT_UTIL_H_
 
 #import <Foundation/Foundation.h>
 
+#include "base/ios/block_types.h"
+
 namespace testing {
 
 // Constant for UI wait loop in seconds.
 extern const NSTimeInterval kSpinDelaySeconds;
 
 // Constant for timeout in seconds while waiting for UI element.
 extern const NSTimeInterval kWaitForUIElementTimeout;
 
 // Constant for timeout in seconds while waiting for JavaScript completion.
 extern const NSTimeInterval kWaitForJSCompletionTimeout;
 
 // Constant for timeout in seconds while waiting for a download to complete.
 extern const NSTimeInterval kWaitForDownloadTimeout;
 
-// Waits until |condition| is true, or induces GREYAssert after |timeout|.
-void WaitUntilCondition(NSTimeInterval timeout, bool (^condition)(void));
-
-// Waits until |condition| is true, or induces GREYAssert after |timeout| with
-// |timeoutDescription| error message.
-void WaitUntilCondition(NSTimeInterval timeout,
-                        NSString* timeoutDescription,
-                        bool (^condition)(void));
+// Returns true when condition() becomes true, otherwise returns false after
+// |timeout|.
+bool WaitUntilConditionOrTimeout(NSTimeInterval timeout,
+                                 ConditionBlock condition);
 
 }  // namespace testing
 
-#endif  // IOS_TESTING_EARL_GREY_WAIT_UTIL_H_
+#endif  // IOS_TESTING_WAIT_UTIL_H_