Preliminary refactoring work on ContextManager.

Preliminary refactoring work on ContextManager.

- There is now a single virtual ContextInfo representing the root of
  the context tree; this should allow us to reduce the need for
  traversing the _contexts map, and should reduce the number of corner
  cases that need to be handled when creating and destroying contexts,
  since tree roots will never be created nor destroyed.

- We now build the contexts while recursing down the directory tree
  and populate them with files while unwinding the recursion; this is
  more consistent with the data flow (deciding which contexts to build
  depends only on the current directory and directories above it;
  deciding which files to include in a context depends only on the
  current directory and directories below it).

R=brianwilkerson@google.com, scheglov@google.com

Committed: https://github.com/dart-lang/sdk/commit/6f6410cd9fcf8a5d7382508b5c8db40a19eea32a

[Paul Berry, 2015-07-21 23:39:45]

paulberry@google.com changed reviewers:
+ scheglov@google.com

[scheglov, 2015-07-22 00:05:51]

LGTM

https://codereview.chromium.org/1243233003/diff/20001/pkg/analysis_server/lib...
File pkg/analysis_server/lib/src/context_manager.dart (right):

https://codereview.chromium.org/1243233003/diff/20001/pkg/analysis_server/lib...
pkg/analysis_server/lib/src/context_manager.dart:366: ContextInfo _ancestorInfo
= new ContextInfo._ancestor();
final?

[Brian Wilkerson, 2015-07-22 13:52:23]

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

[Brian Wilkerson, 2015-07-22 13:52:24]

LGTM

https://codereview.chromium.org/1243233003/diff/20001/pkg/analysis_server/lib...
File pkg/analysis_server/lib/src/context_manager.dart (right):

https://codereview.chromium.org/1243233003/diff/20001/pkg/analysis_server/lib...
pkg/analysis_server/lib/src/context_manager.dart:108: ContextInfo._ancestor()
Perhaps "ContextInfo._root"?

https://codereview.chromium.org/1243233003/diff/20001/pkg/analysis_server/lib...
pkg/analysis_server/lib/src/context_manager.dart:366: ContextInfo _ancestorInfo
= new ContextInfo._ancestor();
Perhaps "_rootInfo"?

[Paul Berry, 2015-07-22 17:31:49]

https://codereview.chromium.org/1243233003/diff/20001/pkg/analysis_server/lib...
File pkg/analysis_server/lib/src/context_manager.dart (right):

https://codereview.chromium.org/1243233003/diff/20001/pkg/analysis_server/lib...
pkg/analysis_server/lib/src/context_manager.dart:108: ContextInfo._ancestor()
On 2015/07/22 13:52:24, Brian Wilkerson wrote:
> Perhaps "ContextInfo._root"?

Acknowledged.  After discussion this morning, I will look into the possibility
of clarifying the nomenclature in a future CL.

https://codereview.chromium.org/1243233003/diff/20001/pkg/analysis_server/lib...
pkg/analysis_server/lib/src/context_manager.dart:366: ContextInfo _ancestorInfo
= new ContextInfo._ancestor();
On 2015/07/22 00:05:51, scheglov wrote:
> final?

Done.

[Paul Berry, 2015-07-22 17:34:47]

Committed patchset #2 (id:20001) manually as
6f6410cd9fcf8a5d7382508b5c8db40a19eea32a (presubmit successful).