add Utils object to provides functions required by Canvas2D tests.
add missing <html> tag.
enable newly added test cases.
replace new Array() with [] to create array object, so that we can even add comma at the last cases. This will be convenient for us to debug test cases.

add Canvas2D case :
 draw convex quadratic bezier curves
 draw concave quadratic bezier curves
 draw rectangle with gradient fill style
 draw rectangle with shadow
 draw patterned rectangle
 draw image
 image data
  this case mainly measure the performance of accessing pixel data, not get/put image data
use a class to package all parameters.