Externs generation: spit out src/-normalized path in generation messages

tools/json_schema_compiler/js_externs_generator.py

 # 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.
 """
 Generator that produces an externs file for the Closure Compiler.
 Note: This is a work in progress, and generated externs may require tweaking.
 
 See https://developers.google.com/closure/compiler/docs/api-tutorial3#externs
 """
 
@@ skipping 19 matching lines @@
 class _Generator(object):
   def __init__(self, namespace):
     self._namespace = namespace
     self._class_name = None
     self._js_util = JsUtil()
 
   def Generate(self):
     """Generates a Code object with the schema for the entire namespace.
     """
     c = Code()
-    (c.Append(self._GetHeader(sys.argv[0], self._namespace.name))
+    # /abs/path/src/tools/json_schema_compiler/
+    script_dir = os.path.dirname(os.path.abspath(__file__))
+    # /abs/path/src/
+    src_root = os.path.normpath(os.path.join(script_dir, '..', '..'))
+    # tools/json_schema_compiler/
+    src_to_script = os.path.relpath(script_dir, src_root)
+    # tools/json_schema_compiler/compiler.py
+    compiler_path = os.path.join(src_to_script, 'compiler.py')
+    (c.Append(self._GetHeader(compiler_path, self._namespace.name))
       .Append())
 
     self._AppendNamespaceObject(c)
 
     for js_type in self._namespace.types.values():
       self._AppendType(c, js_type)
 
     for function in self._namespace.functions.values():
       self._AppendFunction(c, function)
 
@@ skipping 168 matching lines @@
        For example, it might return "chrome.namespace".
 
        Also optionally includes the class name if this is in the context
        of outputting the members of a class.
 
        For example, "chrome.namespace.ClassName.prototype"
     """
     if self._class_name:
       return 'chrome.%s.%s.prototype' % (self._namespace.name, self._class_name)
     return 'chrome.%s' % self._namespace.name