Checkpoint for Response and Tracer: most tests passing.
Checkpoint for global implementation.
Tests working via .global.
More tests working.
Global change notices.
MapChangeRecord
Work on tracing ending.
Only care about change notices if someone is listening.
Tests for new global.
Transform tests are passing.
Error tests passing.
Branching tests pass.
All tests passing.
Merge branch 'master' into tracing

Conflicts:
	lib/runtime/cache.dart
	lib/runtime/transforms.dart
	test/generated/addendum_test.dart
	test/generated/schema_unknown_fields_client.dart
Starting to fit tracing into Multiplexer.
Const factories.
Merge branch 'tracing' into tracing-2
Multiplexer tracing events.
Proxy trace event.
Migrate from dart:json to json pub package