Tiny fix in buildflag.h comment

build/buildflag.h

 // Copyright 2015 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.
 
 #ifndef BUILD_BUILDFLAG_H_
 #define BUILD_BUILDFLAG_H_
 
 // These macros un-mangle the names of the build flags in a way that looks
 // natural, and gives errors if the flag is not defined. Normally in the
 // preprocessor it's easy to make mistakes that interpret "you haven't done
 // the setup to know what the flag is" as "flag is off". Normally you would
 // include the generated header rather than include this file directly.
 //
-// This is for use with generated headers. See build/build_header.gni.
+// This is for use with generated headers. See build/buildflag_header.gni.
 
 // This dance of two macros does a concatenation of two preprocessor args using
 // ## doubly indirectly because using ## directly prevents macros in that
 // parameter from being expanded.
 #define BUILDFLAG_CAT_INDIRECT(a, b) a ## b
 #define BUILDFLAG_CAT(a, b) BUILDFLAG_CAT_INDIRECT(a, b)
 
 // Accessor for build flags.
 //
 // To test for a value, if the build file specifies:
@@ skipping 13 matching lines @@
 // the value in expressions:
 //
 //   const char kSpamServerName[] = BUILDFLAG(SPAM_SERVER_NAME);
 //
 // Because the flag is accessed as a preprocessor macro with (), an error
 // will be thrown if the proper header defining the internal flag value has
 // not been included.
 #define BUILDFLAG(flag) (BUILDFLAG_CAT(BUILDFLAG_INTERNAL_, flag)())
 
 #endif  // BUILD_BUILDFLAG_H_