Support instanceof with declared types in js externs generation

Test: tools/json_schema_compiler/compiler.py -g externs extensions/common/api/automation.idl > third_party/closure_compiler/externs/automation.js
results in no diffs. automation.js was hand edited previously.
Run
tools/json_schema_compiler/js_externs_generator_test.py

Change-Id: I949530eecb24e5a26bc2f5bff13c831bdad3dbbf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2314016
Commit-Queue: David Tseng <dtseng@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#791533}

tools/json_schema_compiler/js_externs_generator_test.py

@@ -84,6 +84,8 @@ namespace fakeApi {
 
     static void instanceOfObjectParam([instanceOf=SomeType] object obj);
 
+    static void instanceOfBarObjectParam([instanceOf=Bar] object barObj);
+
     static void optionalParam(optional OptionalParamCallback callback);
 
     static void nonFinalOptionalParams(
@@ -241,6 +243,12 @@ chrome.fakeApi.returnString = function() {};
  */
 chrome.fakeApi.instanceOfObjectParam = function(obj) {};
 
+/**
+ * @param {chrome.fakeApi.Bar} barObj
+ * @see https://developer.chrome.com/extensions/fakeApi#method-instanceOfBarObjectParam
+ */
+chrome.fakeApi.instanceOfBarObjectParam = function(barObj) {};
+
 /**
  * @param {function((!chrome.fakeApi.Qux|undefined)): void=} callback
  * @see https://developer.chrome.com/extensions/fakeApi#method-optionalParam

tools/json_schema_compiler/js_util.py

@@ -163,7 +163,14 @@ class JsUtil(object):
         c = Code()
         self.AppendObjectDefinition(c, namespace_name, js_type.properties)
         return c
+
+      # Support instanceof for types in the same namespace and built-in
+      # types. This doesn't support types in another namespace e.g. if
+      # js_type.instanceof is 'tabs.Tab'.
       if js_type.instance_of:
+        if js_type.instance_of in js_type.namespace.types:
+          return Code().Append('chrome.%s.%s' %
+                               (namespace_name, js_type.instance_of))
         return Code().Append(js_type.instance_of)
       return Code().Append('Object')
     if js_type.property_type is PropertyType.ARRAY: