Add StrictTypeChecking to CRC2D.{drawImage,createPattern}

This moves the null-check out into generated bindings code.
The non-standard method drawImageFromRect(...) keeps the null-check,
and has its first argument marked nullable because of that.

Review URL: https://codereview.chromium.org/232313004

git-svn-id: svn://svn.chromium.org/blink/trunk@171477 bbb929c8-8fbe-4397-9dbb-9b2b20218538