Add support for type checking of floating point arguments as [TypeChecking=Unrestricted]

This adds an new extended attribute value, [TypeChecking=Unrestricted],
which turns on type checking of floating point arguments for non-finite
values, and switches CanvasRenderingContext2D.createImageData over as a
test case.

This does not implement type-checking for floating point attributes yet.

Docs updated at:
http://www.chromium.org/blink/webidl/blink-idl-extended-attributes#TOC-TypeChecking-i-m-a-

R=haraken
R=fs
BUG=354298
BUG=367648
TEST=run_webkit_tests.sh fast/canvas/canvas-2d-imageData-create-nonfinite.html

Review URL: https://codereview.chromium.org/259773008

git-svn-id: svn://svn.chromium.org/blink/trunk@172945 bbb929c8-8fbe-4397-9dbb-9b2b20218538