Identity extension API impl: Split constants into their own file

chrome/browser/extensions/api/identity/identity_api.h

Index: chrome/browser/extensions/api/identity/identity_api.h
diff --git a/chrome/browser/extensions/api/identity/identity_api.h b/chrome/browser/extensions/api/identity/identity_api.h
index 836da938499a99ba29b070fa5114bb9a92c49692..b39ae4152c2d3a5f969760db26ee0ecb05255f2b 100644
--- a/chrome/browser/extensions/api/identity/identity_api.h
+++ b/chrome/browser/extensions/api/identity/identity_api.h
@@ -42,20 +42,6 @@ namespace extensions {
 class GetAuthTokenFunctionTest;
 class MockGetAuthTokenFunction;
 
-namespace identity_constants {
-extern const char kInvalidClientId[];
-extern const char kInvalidScopes[];
-extern const char kAuthFailure[];
-extern const char kNoGrant[];
-extern const char kUserRejected[];
-extern const char kUserNotSignedIn[];
-extern const char kInteractionRequired[];
-extern const char kInvalidRedirect[];
-extern const char kOffTheRecord[];
-extern const char kPageLoadFailure[];
-extern const char kCanceled[];
-}  // namespace identity_constants
-
 class IdentityTokenCacheValue {
  public:
   IdentityTokenCacheValue();