Fix direct event type querying by using a generic event wrapper function

[Abhishek Arya]

As per Dimitri's comments on bug https://bugs.webkit.org/show_bug.cgi?id=48345, we should prevent direct event-type() querying in various places e.g.

void ImageEventListener::handleEvent(ScriptExecutionContext*, Event* event)
{
    if (event->type() == eventNames().resizeEvent)
        m_doc->windowSizeChanged();
    else if (event->type() == eventNames().clickEvent) {
        MouseEvent* mouseEvent = static_cast<MouseEvent*>(event);

And replace with a generic wrapper like isMouseClickEvent(event) which does the
1) event type check - event->type() == eventNames().clickEvent
2) event cast check - event->isMouseEvent

[Ahmad Saleem]

When searching for "ImageEventListener", I can only find single source in Webkit Github:

https://github.com/WebKit/WebKit/blob/50d7e0b0b808afca93e5ede9cd7c0d44b1ed8130/Source/WebCore/html/ImageDocument.cpp#L62

Is this in relation to above? Or this is no longer applicable. Thanks!

[Alexey Proskuryakov]

We don't have this idea implemented, but we use safer casting. I'll leave it to others to decide if this is still worth tracking. Currently, the code looks like this:

void ImageEventListener::handleEvent(ScriptExecutionContext&, Event& event)
{
    if (event.type() == eventNames().resizeEvent)
        m_document.windowSizeChanged();
    else if (event.type() == eventNames().clickEvent && is<MouseEvent>(event)) {
        MouseEvent& mouseEvent = downcast<MouseEvent>(event);