
Support full canvas spec that allows for additional args to getContext

R=nicksantos
DELTA=2  (1 added, 0 deleted, 1 changed)


Revision created by MOE tool push_codebase.
MOE_MIGRATION=226177


ajukraine/closure-compiler,olegshnitko/closure-compiler,ajukraine/closure-compiler,olegshnitko/closure-compiler