Refine types in _JsonMap to avoid getInterceptor calls
Refine types in _JsonMap to avoid getInterceptor calls

This change avoids getInterceptor calls on `_data` inside most _JsonMap methods.

R=kasperl@google.com

Review URL: https://codereview.chromium.org//384883002

git-svn-id: c93d8a2297af3b929165606efe145742a534bc71@38169 260f80e4-7a28-3924-810f-c04153c831b5

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