Support PNG and quality control in chrome.tabs.captureVisibleTab().

chrome/browser/extensions/extension_function.cc

Index: chrome/browser/extensions/extension_function.cc
diff --git a/chrome/browser/extensions/extension_function.cc b/chrome/browser/extensions/extension_function.cc
index 006fe9986425be7c8ca7ea55c25a8f7259c57883..f3193155914a5afa9d08d2b2201247151f2d9798 100644
--- a/chrome/browser/extensions/extension_function.cc
+++ b/chrome/browser/extensions/extension_function.cc
@@ -1,4 +1,4 @@
-// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Copyright (c) 2010 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.
 
@@ -31,6 +31,13 @@ void AsyncExtensionFunction::SendResponse(bool success) {
   }
 }
 
+bool AsyncExtensionFunction::HasOptionalArgument(size_t index) {
+  DCHECK(args_->IsType(Value::TYPE_LIST));
+  ListValue* args_list = static_cast<ListValue*>(args_.get());
+  Value* value;
+  return args_list->Get(index, &value) && !value->IsType(Value::TYPE_NULL);
+}
+
 std::string AsyncExtensionFunction::extension_id() {
   DCHECK(dispatcher());
   return dispatcher()->extension_id();