Android: Fix for performance issue with WebViews

[scottrules44]

Fix for Issue #287,
There is a slight performance issue with Android WebViews when "alpha" property is used before the page has loaded
See example below

`function showWebView(URL)
local loadingMessage, webView = nil, nil
local x, y = display.safeScreenOriginX + display.safeActualContentWidth/2, display.safeScreenOriginY + display.safeActualContentHeight/2

local function webListener( event )
if event.type == "loaded" then

  transition.to( webView, { time = 600, alpha = 1 } )
  transition.to( loadingMessage, { time = 400, alpha = 0 } )
end

end

loadingMessage = display.newText({parent = webPopup, text = "LOADING PLEASE WAIT....", x = x, y = y, width = 400, font = native.systemFontBold, fontSize = 15, align = "left"})

webView = native.newWebView( x, y, display.safeActualContentWidth, display.safeActualContentHeight )
webView:request( URL )
webView.alpha = 0
webView:addEventListener( "urlRequest", webListener )
end

showWebView("https://catinfo.org")`