Fix accessibility constant clash in OSX 10.12.

content/browser/accessibility/browser_accessibility_cocoa.mm

Index: content/browser/accessibility/browser_accessibility_cocoa.mm
diff --git a/content/browser/accessibility/browser_accessibility_cocoa.mm b/content/browser/accessibility/browser_accessibility_cocoa.mm
index 900686dcea03ba6b1791b4ad7ce9006b0a793139..ce288f3ead4ced19890084e5974b02aea2c73621 100644
--- a/content/browser/accessibility/browser_accessibility_cocoa.mm
+++ b/content/browser/accessibility/browser_accessibility_cocoa.mm
@@ -53,7 +53,10 @@ NSString* const NSAccessibilityInvalidAttribute = @"AXInvalid";
 NSString* const NSAccessibilityIsMultiSelectableAttribute =
     @"AXIsMultiSelectable";
 NSString* const NSAccessibilityLoadingProgressAttribute = @"AXLoadingProgress";
-NSString* const NSAccessibilityRequiredAttribute = @"AXRequired";
+#if !defined(MAC_OS_X_VERSION_10_12) || \
+    MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_X_VERSION_10_12
+  NSString* const NSAccessibilityRequiredAttribute = @"AXRequired";

[erikchen, 2016/08/19 00:59:00]

whoops, shouldn't have had 2 spaces at the beginning of the line. My bad. You
can use "git cl format" to auto-format your CL to deal with these pesky nits.

[pwnall, 2016/08/19 01:27:43]

Done.

+#endif
 NSString* const
     NSAccessibilityUIElementCountForSearchPredicateParameterizedAttribute =
         @"AXUIElementCountForSearchPredicate";