Fix incremental resolution of files referenced by multiple contexts.
Fix incremental resolution of files referenced by multiple contexts.

There were two problems:

1. When a file was set as a priority, we weren't propagating that
information to all contexts; as a result, the resolved AST wasn't
cached in all contexts, so incremental resolution wasn't able to take
place in all contexts.

2. In setPriorityFiles we weren't scheduling analysis operations, so
even after the file was made a priority, its resolved AST wouldn't be
available until some other event triggered analysis in that context.

BUG=dartbug.com/22209
R=scheglov@google.com

Review URL: https://codereview.chromium.org//892493003

git-svn-id: c93d8a2297af3b929165606efe145742a534bc71@43323 260f80e4-7a28-3924-810f-c04153c831b5

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-archive/dart-sdk