Move EarlGrey helper to check toolbar visibility into ChromeEarlGreyUI.

ios/chrome/test/earl_grey/chrome_earl_grey_ui.h

Index: ios/chrome/test/earl_grey/chrome_earl_grey_ui.h
diff --git a/ios/chrome/test/earl_grey/chrome_earl_grey_ui.h b/ios/chrome/test/earl_grey/chrome_earl_grey_ui.h
index 792001a296045542e2b72992ec74ce3dfd50f454..aee3b866e38865de7488217963461b0d37b0b1ed 100644
--- a/ios/chrome/test/earl_grey/chrome_earl_grey_ui.h
+++ b/ios/chrome/test/earl_grey/chrome_earl_grey_ui.h
@@ -29,6 +29,11 @@
 // Requires having a tab opened.
 + (void)openShareMenu;
 
+// Waits for toolbar to become visible if |isVisible| is YES, or waits for it
+// to disappear if |isVisible| is NO. Induces a GREYAssert if the condition is
+// not met after a timeout.
++ (void)waitForToolbarVisible:(BOOL)isVisible;
+
 @end
 
 #endif  // IOS_CHROME_TEST_EARL_GREY_CHROME_EARL_GREY_UI_H_