a2ff93da67
In order to un-block Flutter integration, we introduce partial support for conditional imports into the CFE. There are two incomplete parts: - The condition strings are evaluated by the Target. They should be looked up in the environment, but this introduces complications with modular compilation. - Type inference and other static checks are performed with reference to the implementation (conditionally-imported) library rather than the interface library. See issue #30143 for more details. Bug: Change-Id: I740b45e9d32796644837de4caefd8d6e8015f229 Reviewed-on: https://dart-review.googlesource.com/34721 Reviewed-by: Peter von der Ahé <ahe@google.com>