Update cef_api_hash.h at build time if necessary (fixes issue #2922)

The cef_api_hash.h file was previously only updated when the translator tool
was run manually. Forgetting to run the translator tool after changing
include/internal/cef_types*.h files would result in cef_parser.py
incorrectly computing the CEF minor version number for future builds. By
updating this file automatically at build time the number of errors should be
reduced.

tools/make_pack_header.py

@@ -119,16 +119,7 @@ def MakeFile(output, input):
   guard = 'CEF_INCLUDE_' + filename.replace('.', '_').upper() + '_'
   result = result.replace('$GUARD$', guard)
 
-  if path_exists(output):
-    old_contents = read_file(output)
-  else:
-    old_contents = ''
-
-  if (result != old_contents):
-    write_file(output, result)
-    sys.stdout.write('File ' + output + ' updated.\n')
-  else:
-    sys.stdout.write('File ' + output + ' is already up to date.\n')
+  write_file_if_changed(output, result)
 
 
 def main(argv):