Add rendering fast path for when playing a display list canvas at 1:1 scale

This patch modifies GraphicsContext::drawPicture to make it
avoid the use of image filters for presenting canvas
contents, and just use a plain save layer when drawing
contents at 1:1 pixel scale.

BUG=386601

Review URL: https://codereview.chromium.org/662673002

git-svn-id: svn://svn.chromium.org/blink/trunk@183836 bbb929c8-8fbe-4397-9dbb-9b2b20218538