Copy files for splitting src/compiler.dart into several libraries

Copy files for splitting src/compiler.dart into several libraries

Intended future content:

common/backend_api.dart:
  Backend

common/codegen.dart:
  CodegenRegistry
  CodegenWorkItem

common/registry.dart:
  Registry

common/resolution.dart:
  ResolutionCallbacks
  ResolutionWorkItem

common/tasks.dart:
  CompilerTask
  DeferredAction
  DeferredTask,
  GenericTask

common/work.dart:
  ItemCompilationContext
  WorkItem

diagnostics/code_location.dart:
  AnyLocation
  CodeLocation
  PackageLocation
  SchemeLocation

diagnostics/invariant.dart:
  DEBUG_MODE
  assertDebugMode
  invariant
  REPORT_EXCESS_RESOLUTION

diagnostics/source_span.dart
  SourceSpan

diagnostics/spannable.dart
  Spannable (from util/util.dart)
  NO_LOCATION_SPANNABLE (from util/util.dart)
  CURRENT_ELEMENT_SPANNABLE (from util/util.dart)

scanner/token_map:
  TokenKey
  TokenMap

BUG=
R=sigmund@google.com

Committed: https://github.com/dart-lang/sdk/commit/1d0bc4b94ee8050fde64a4459a371aad781a2b71

[Johnni Winther, 2015-08-10 14:46:22]

johnniwinther@google.com changed reviewers:
+ karlklose@google.com

[Siggi Cherem (dart-lang), 2015-08-10 16:28:59]

sigmund@google.com changed reviewers:
+ sigmund@google.com

[Siggi Cherem (dart-lang), 2015-08-10 16:28:59]

lgtm - is the copy to make it easier to track history?

I'd be fine just splitting the files in a single CL too.

[Johnni Winther, 2015-08-11 07:52:04]

On 2015/08/10 16:28:59, Siggi Cherem (dart-lang) wrote:
> lgtm - is the copy to make it easier to track history?

Yes. (And easier reviewing of the follow-up)

[Johnni Winther, 2015-08-11 08:57:22]

Committed patchset #1 (id:1) manually as
1d0bc4b94ee8050fde64a4459a371aad781a2b71 (presubmit successful).