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

chrome/browser/extensions/extension_function.cc

-// 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.
 
 #include "chrome/browser/extensions/extension_function.h"
 
 #include "base/json/json_writer.h"
 #include "base/logging.h"
 #include "chrome/browser/extensions/extension_function_dispatcher.h"
 
 void AsyncExtensionFunction::SetArgs(const Value* args) {
@@ skipping 12 matching lines @@
 void AsyncExtensionFunction::SendResponse(bool success) {
   if (!dispatcher())
     return;
   if (bad_message_) {
     dispatcher()->HandleBadMessage(this);
   } else {
     dispatcher()->SendResponse(this, 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();
 }
 
 Profile* AsyncExtensionFunction::profile() const {
   DCHECK(dispatcher());
   return dispatcher()->profile();
 }