Convert SecurityError exceptions to 'es.throwSecurityError()'.

This patch moves several SecurityError exceptions over to the new API,
and adds comments to the code to make it clear why URLs are exposed to
JavaScript in the cases where a URL is exposed.

BUG=275282

Review URL: https://chromiumcodereview.appspot.com/23283009

git-svn-id: svn://svn.chromium.org/blink/trunk@156298 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Improve 'HTMLCanvasElement.toDataURL()' SecurityError message.

BUG=152212

Review URL: https://chromiumcodereview.appspot.com/22846006

git-svn-id: svn://svn.chromium.org/blink/trunk@156299 bbb929c8-8fbe-4397-9dbb-9b2b20218538