js_codegen.dart and patch_sdk.dart are the only human-changed files.
This also pulls in dart:isolate, which is depended on from one of the implementation libraries
This also moves dart:_* files back to `lib/_internal/compiler/js_lib/` because there's where libraries.dart points to, and hence Analyzer looks for them there. Alternatively, we could put them somewhere like `tool/input_sdk_internal` and then copy that file into the right path.
R=vsm@google.com
Review URL: https://codereview.chromium.org/955513008
John Messerly