handleBrowserEvent: don't compute mouseposition if it's not needed

[fredj]

OpenLayers.Events.handleBrowserEvent compute the mouse position if includeXY is true but don't check if a listener is registered on the event type.

[erilem]

addEventType initializes the type's listeners array to [], so I think we should do

var listeners = this.listeners[evt.type];
if(listeners && listeners.length > 0) {
    if (this.includeXY) {
        evt.xy = this.getMousePosition(evt);
    }
    this.triggerEvent(evt.type, evt);
}

just like what triggerEvent itself does.

[erilem]

2880.1.patch

See the following FireBug profile results. Experiments involve panning the map using tilecache.html in full page.

Without patch
--------------
positionImage() 156 16.38%
toFloat() 12612	12.75%
triggerEvent() 3164 6.35%
centerLayerContainer() 211 5.58%
initialize() 2590 4.29%
handleBrowserEvent() 2234 3.54%
getMousePosition() 1120 3.11%

With patch
----------
positionImage()	150 16.61%
toFloat() 12406	12.46%
triggerEvent() 1874 5.67%
centerLayerContainer() 197 5.38%
initialize() 2532 4.58%
getMousePosition() 988 3.52%

With the patch, triggerEvent and getMousePosition are significantly less called.

Except Request.html (#2913) and Popup.html (#2919), all tests pass in FF3. The failing tests are unrelated to this patch, they fail even when this patch isn't applied.

fredj, please commit if you agree with 2880.1.patch .

[fredj]

r10873