[Selenium]计算坐标进行拖拽，重写dragAndDropOffset

//@author jzhang6
	public void dragAndDropOffset(WebDriver driver,WebElement dragableEl, WebElement dropableEl, int offsetX, int offsetY){
		Actions action = new Actions(driver);
		action.clickAndHold(dragableEl).build().perform();
		action.moveByOffset(offsetX, offsetY);
		action.release(dropableEl);
		action.build().perform();
	}

//@author jzhang6
	public void dragWidget(String widgetName){
		WebElement widgetIconEl=page.getWidgetIconInDockMenu(widgetName);
		((JavascriptExecutor) driver).executeScript("arguments[0].scrollIntoView();", widgetIconEl);

		WebElement workspaceEl=page.getWorkSpace();
		Point initialPositon = widgetIconEl.getLocation();
		Point targetPositon = workspaceEl.getLocation();
		int offsetX = (targetPositon.getX() - initialPositon.getX())/2;
		int offsetY = (targetPositon.getY() - initialPositon.getY())/2;
		System.out.println("Drag widget to : ("+offsetX+","+offsetY+")");

		WebElement dropableEl=page.getDropableIconInWorkspace();

		this.dragAndDropOffset(driver,widgetIconEl,dropableEl,offsetX, offsetY);

		SeleniumUtil.waitUntilAllAjaxRequestCompletes(driver);
		this.waitForLoadingDoneInNewWebPage(driver);
	}