Refactor wait_util so it isn't coupled to EarlGrey.

ios/testing/wait_util.h

Index: ios/testing/wait_util.h
diff --git a/ios/testing/earl_grey/wait_util.h b/ios/testing/wait_util.h
similarity index 56%
copy from ios/testing/earl_grey/wait_util.h
copy to ios/testing/wait_util.h
index 33df9252ec54271c8ab1230833b40dd5d0d658a3..f162a74faa63a54861d6741ff23ab80fee8a95c3 100644
--- a/ios/testing/earl_grey/wait_util.h
+++ b/ios/testing/wait_util.h
@@ -2,11 +2,13 @@
 // 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.
@@ -21,15 +23,11 @@ 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_