addJavascriptHandler method
Implementation
void addJavascriptHandler(String name, JavascriptHandlerCallback callback) {
assert(!_javascriptChannelMap.containsKey(name));
_javascriptChannelMap[name] = callback;
}
void addJavascriptHandler(String name, JavascriptHandlerCallback callback) {
assert(!_javascriptChannelMap.containsKey(name));
_javascriptChannelMap[name] = callback;
}