Test to catch Canvas 2D API changes. If this test should ever fail, we should re-examine the Canvas 2D state saving/restoring logic in the InjectedScriptModule to include any latest changes to the API.

New properties and functions that should be manually examined (should be empty to pass the test):
addHitRegion
clearHitRegions
currentTransform
drawFocusIfNeeded
ellipse
isContextLost
removeHitRegion
resetTransform
scrollPathIntoView
webkitImageSmoothingEnabled
New properties and functions of CanvasGradient object that should be manually examined (should be empty to pass the test):
New properties and functions of CanvasPattern object that should be manually examined (should be empty to pass the test):