Add js_interface_generator for generating extensions interfaces

tools/json_schema_compiler/code.py

 # Copyright (c) 2012 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.
 
 class Code(object):
   """A convenience object for constructing code.
 
   Logically each object should be a block of code. All methods except |Render|
   and |IsEmpty| return self.
   """
@@ skipping 11 matching lines @@
     """Appends a line of code at the current indent level or just a newline if
     line is not specified.
 
     substitute: indicated whether this line should be affected by
     code.Substitute().
     new_line: whether this should be added as a new line, or should be appended
         to the last line of the code.
     strip_right: whether or not trailing whitespace should be stripped.
     """
 
-    prefix = indent_level * ' ' if indent_level else ''.join(
-        self._line_prefixes)
+    if line:
+      prefix = indent_level * ' ' if indent_level else ''.join(
+          self._line_prefixes)
+    else:
+      prefix = ''
 
     if strip_right:
       line = line.rstrip()
 
     if not new_line and self._code:
       self._code[-1].value += line
     else:
       self._code.append(Line(prefix + line, substitute=substitute))
     return self
 
@@ skipping 119 matching lines @@
       if self._code[i].substitute:
         # Only need to check %s because arg is a dict and python will allow
         # '%s %(named)s' but just about nothing else
         if '%s' in self._code[i].value or '%r' in self._code[i].value:
           raise TypeError('"%s" or "%r" found in substitution. '
                           'Named arguments only. Use "%" to escape')
         self._code[i].value = line.value % d
         self._code[i].substitute = False
     return self
 
+  def TrimTrailingNewlines(self):
+    """Trims any trailing newlines.

[Dan Beam, 2015/12/10 22:17:33]

i'm confused by this code, but have you seen rstrip()?

[stevenjb, 2015/12/10 22:29:04]

self._code is an array of Line objects. This removes empty Line objects at the
end. The comment could be better.

+    """
+    while self._code:
+      if self._code[-1].value != '':
+        return
+      self._code = self._code[:-1]
+
   def Render(self):
     """Renders Code as a string.
     """
     return '\n'.join([l.value for l in self._code])
 
 
 class Line(object):
   """A line of code.
   """
   def __init__(self, value, substitute=True):
     self.value = value
     self.substitute = substitute