Generate externs automatically from json/idl files: minor changes.

tools/json_schema_compiler/compiler.py

Index: tools/json_schema_compiler/compiler.py
diff --git a/tools/json_schema_compiler/compiler.py b/tools/json_schema_compiler/compiler.py
index 38899286d215158c7701ff7cda84285f927e0f01..0b33431de0fe6b16926254ccf301cddb87605ea8 100755
--- a/tools/json_schema_compiler/compiler.py
+++ b/tools/json_schema_compiler/compiler.py
@@ -24,13 +24,15 @@ from cpp_bundle_generator import CppBundleGenerator
 from cpp_generator import CppGenerator
 from cpp_type_generator import CppTypeGenerator
 from dart_generator import DartGenerator
+from js_externs_generator import JsExternsGenerator
 import json_schema
 from model import Model
 from schema_loader import SchemaLoader
 
 # Names of supported code generators, as specified on the command-line.
 # First is default.
-GENERATORS = ['cpp', 'cpp-bundle-registration', 'cpp-bundle-schema', 'dart']
+GENERATORS = ['cpp', 'cpp-bundle-registration', 'cpp-bundle-schema', 'dart',
+              'externs']
 
 def GenerateSchema(generator_name,
                    file_paths,
@@ -115,8 +117,12 @@ def GenerateSchema(generator_name,
       ('%s.dart' % namespace.unix_name, DartGenerator(
           dart_overrides_dir))
     ]
+  elif generator_name == 'externs':
+    generators = [
+      ('%s_externs.js' % namespace.unix_name, JsExternsGenerator())
+    ]
   else:
-    raise Exception('Unrecognised generator %s' % generator)
+    raise Exception('Unrecognised generator %s' % generator_name)
 
   output_code = []
   for filename, generator in generators: