[util] Identation fixes in ImageUtils
[widget] Cancel image requests when TweetElement is dettached
[canvas] Add isAttachedToHost() to UIElement interface
[async] Update/fix comments in AsyncTweetElement
[canvas] Use getResources() in TextElement
[async] Set UIElement before updating it in AsyncTweetView
[canvas] Use getResources() in ImageElement
[canvas] Properly handle dettached case in ImageElement
[async] Remove default host from AsyncTweetElement