By Applying this Code Snippet you will be able to re-size Windows Phone Web Browser To Fit Content.
<phone:WebBrowser x:Name="myBrowser" IsHitTestVisible="True" IsScriptEnabled="True" Foreground="Gray" ScriptNotify="myBroswer_ScriptNotify" LoadCompleted="myBroswer_LoadCompleted" NavigationFailed="wbDetails_NavigationFailed" />
private void myBrowser_ScriptNotify(object sender, NotifyEventArgs e)
{
WebBrowser thisBrowser = (WebBrowser)sender;
int height = Convert.ToInt32(e.Value);
double newHeight = height * 1.5;
thisBrowser.Height = newHeight;
}