This CL changes dart2js such that the effect that we used to get with
option '--initializing-formal-access' is now obtained unconditionally,
i.e., that extension is now enabled by default.
dart2js will continue to accept the option, such that scripts passing
the option will not break.
The CL is _not_ intended to be landed at this time, the plan is to
enable the feature in a coordinated manner when all tools are ready.
R=johnniwinther@google.com
Review URL: https://codereview.chromium.org/2141023002 .
Brian Wilkerson