[Extension API Extern Generation] Add support for function types

tools/json_schema_compiler/js_externs_generator_test.py

 #!/usr/bin/env python
 # 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.
 
 import idl_schema
 from js_externs_generator import JsExternsGenerator
 from datetime import datetime
 import model
 import unittest
@@ skipping 28 matching lines @@
     Bar[]? optionalObjArr;
     Greek[] enumArr;
     any[] anythingGoes;
     Bar obj;
     long? maybe;
     (DOMString or Greek or long[]) choice;
   };
 
   callback VoidCallback = void();
 
+  callback BazGreekCallback = void(Baz baz, Greek greek);
+
   interface Functions {
-    // Does something exciting!
+    // Does something exciting! And what's more, this is a multiline function
+    // comment! It goes onto multiple lines!
     // |baz| : The baz to use.
-    static void doSomething(Baz baz, optional VoidCallback callback);
+    static void doSomething(Baz baz, VoidCallback callback);
+
+    static void bazGreek(optional BazGreekCallback callback);
+
+    [deprecated="Use a new method."] static DOMString returnString();
   };
 };
 """
 
 # The output we expect from our fake idl file.
 expected_output = """// Copyright %s 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.
 
 /** @fileoverview Externs generated from namespace: fakeApi */
@@ skipping 32 matching lines @@
  *   enumArr: !Array<!chrome.fakeApi.Greek>,
  *   anythingGoes: !Array<*>,
  *   obj: Bar,
  *   maybe: (number|undefined),
  *   choice: (string|!chrome.fakeApi.Greek|!Array<number>)
  * }}
  */
 var Baz;
 
 /**
- * Does something exciting!
+ * Does something exciting! And what's more, this is a multiline function
+ * comment! It goes onto multiple lines!
  * @param {Baz} baz The baz to use.
- * @param {Function=} callback
+ * @param {function():void} callback
  */
 chrome.fakeApi.doSomething = function(baz, callback) {};
+
+/**
+ * @param {function(Baz, !chrome.fakeApi.Greek):void=} callback
+ */
+chrome.fakeApi.bazGreek = function(callback) {};
+
+/**
+ * @return {string}
+ * @deprecated Use a new method.
+ */
+chrome.fakeApi.returnString = function() {};
 """ % datetime.now().year
 
 
 class JsExternGeneratorTest(unittest.TestCase):
   def testBasic(self):
     self.maxDiff = None # Lets us see the full diff when inequal.
     filename = 'fake_api.idl'
     api_def = idl_schema.Process(fake_idl, filename)
     m = model.Model()
     namespace = m.AddNamespace(api_def[0], filename)
     self.assertMultiLineEqual(expected_output,
                               JsExternsGenerator().Generate(namespace).Render())
 
 
 if __name__ == '__main__':
   unittest.main()