Make EarlGrey matchers compliant with Chromium style.

ios/testing/earl_grey/matchers.mm

 // 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.
 
 #import "ios/testing/earl_grey/matchers.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
 namespace testing {
 
-id<GREYMatcher> contextMenuItemWithText(NSString* text) {
+id<GREYMatcher> ContextMenuItemWithText(NSString* text) {
   // Both tablet and phone house context menu views inside an alert controller
   // view (on tablet that view is itself inside a popover view).
   id<GREYMatcher> context_menu_container =
       grey_kindOfClass(NSClassFromString(@"_UIAlertControllerView"));
 
   return grey_allOf(grey_ancestor(context_menu_container), grey_interactable(),
                     grey_text(text), nil);
 }
 
-id<GREYMatcher> elementToDismissContextMenu(NSString* cancel_text) {
+id<GREYMatcher> ElementToDismissContextMenu(NSString* cancel_text) {
   UIUserInterfaceIdiom idiom = [[UIDevice currentDevice] userInterfaceIdiom];
   if (idiom == UIUserInterfaceIdiomPad) {
     // On iPad the context menu is dismissed by tapping on something
     // that isn't the popover. UIKit conveniently labels this element.
     return grey_accessibilityID(@"PopoverDismissRegion");
   } else {
     // On iPhone the context menu is dismissed by tapping on the "Cancel" item.
-    return contextMenuItemWithText(cancel_text);
+    return ContextMenuItemWithText(cancel_text);
   }
 }
 
 }  // namespace testing