Closure conversion

[peter-ahe-google]

Meta issue for tracking known issues in closure conversion.

• [x] VM assertion error: expected: !is_cycle_free() #38.
• [x] for loops #32.
• [x] capture this.
• [x] static tear-off methods #39.
• [x] super calls #35.
• [x] type variables #36.
• [ ] tear-off methods #34.
• [ ] use VM context and function pointers #37.

[karlklose]

This issue was moved to dart-lang/sdk#28126