Separate the API's used by ContextManager.

Separate the API's used by ContextManager.

Previously, ContextManager had two API's: one used by analysis server
to tell the ContextManager what to do, and one used by the
ContextManager to make callbacks to analysis server in response to its
requests.  The first API was implemented in the class
AbstractContextManager, which derived from ContextManager, and the
second API was implemented in ServerContextManager, which derived from
AbstractContextManager.

In addition to causing confusion, this made it impossible to provide
an alternate implementation of ContextManager as a plug-in, since the
plug in would have had to re-implement the second API, and that would
have required accessing private implementation details of the
ContextManager.

This CL separates the API's: the first API is specified in
ContextManager and implemented in ContextManagerImpl, and the second
API is specified in ContextManagerCallbacks and implemented in
ServerContextManagerCallbacks.

In the long run I hope to eliminate the ContextManagerCallbacks class
entirely, by having the ContextManager tell its client what to do
using return values rather than callbacks.

R=brianwilkerson@google.com

Committed: https://github.com/dart-lang/sdk/commit/128dec84b5528d268cb25d622a3ea0dd5a9332e9

[Paul Berry, 2015-07-20 22:56:13]

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

[Brian Wilkerson, 2015-07-21 13:56:44]

LGTM

https://codereview.chromium.org/1243893002/diff/1/pkg/analysis_server/lib/src...
File pkg/analysis_server/lib/src/analysis_server.dart (right):

https://codereview.chromium.org/1243893002/diff/1/pkg/analysis_server/lib/src...
pkg/analysis_server/lib/src/analysis_server.dart:355: (contextManager.callbacks
as ServerContextManagerCallbacks).onContextsChanged;
Do we plan on eventually removing the need for this cast, such as by defining
'onContextsChanged' on ContextManagerCallbacks or by removing the need to call
it?

[Paul Berry, 2015-07-21 17:22:21]

https://codereview.chromium.org/1243893002/diff/1/pkg/analysis_server/lib/src...
File pkg/analysis_server/lib/src/analysis_server.dart (right):

https://codereview.chromium.org/1243893002/diff/1/pkg/analysis_server/lib/src...
pkg/analysis_server/lib/src/analysis_server.dart:355: (contextManager.callbacks
as ServerContextManagerCallbacks).onContextsChanged;
On 2015/07/21 13:56:44, Brian Wilkerson wrote:
> Do we plan on eventually removing the need for this cast, such as by defining
> 'onContextsChanged' on ContextManagerCallbacks or by removing the need to call
> it?

Yes.  My plan (probably in the next CL) is to remove the need for this cast by
moving defaultOptions and onContextsChanged into AnalysisServer.  I've added
TODO comments to make the plan clear.

[Paul Berry, 2015-07-21 17:41:01]

Committed patchset #1 (id:1) manually as
128dec84b5528d268cb25d622a3ea0dd5a9332e9 (presubmit successful).