dart2js: Allow read-only access to initializing formals.

[eernstg]

This is the dart2js specific issue for #26655. That issue has the details.

[eernstg]

This extension is supported by dart2js starting from commit c3dfe51, behind the flag --initializing-formal-access.

[eernstg]

The semantics has been adjusted such that the initializing formal parameter is in scope in the initalizer list, but not in the body. The implementation in c3dfe51 implements the old semantics.

[eernstg]

As of commit 6942e0d, dart2js has been adjusted to implement the scoping where initializing formals are in scope in the initializer list, but not in the body.

[eernstg]

The CL https://codereview.chromium.org/2141023002/ will make the effect of '--initializing-formal-access' the default behavior of dart2js. The intention is that this CL will be landed when all tools are ready to make support for initializing formal access the default.

[eernstg]

Closing: Enabling the feature by default has now been split out into a separate issue #27893.