Refactor wait_util so it isn't coupled to EarlGrey.

ios/testing/earl_grey/wait_util.h

Index: ios/testing/earl_grey/wait_util.h
diff --git a/ios/testing/earl_grey/wait_util.h b/ios/testing/earl_grey/wait_util.h
index 33df9252ec54271c8ab1230833b40dd5d0d658a3..318b1ff08c5b625940edc902e7c59b987ccef817 100644
--- a/ios/testing/earl_grey/wait_util.h
+++ b/ios/testing/earl_grey/wait_util.h
@@ -9,18 +9,6 @@
 
 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));