Fix "reanalyze sources" when there are unsaved files.

Fix "reanalyze sources" when there are unsaved files.

The analysis server now maintains a single content cache which is
shared by all contexts; this allows it to persist the content cache
across reanalysis (which destroys all contexts and recreates them from
scratch).

Two other bugs are fixed in the process:

- If a file is analyzed in multiple contexts, then editing it will
  cause all affected contexts to be notified of the change.  (Note
  that this could potentially account for some other strange behaviors
  we've seen recently, such as incorrect semantic highlighting and
  lingering errors/warnings.)

- If the client supplies a ChangeContentOverlay for a file which
  currently has no overlay, the proper error is generated.

I plan to submit tests for these two bugs in a follow-up CL.

R=brianwilkerson@google.com

Committed: https://code.google.com/p/dart/source/detail?r=43163

[Paul Berry, 2015-01-26 22:43:21]

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

[Brian Wilkerson, 2015-01-26 23:05:02]

LGTM

https://codereview.chromium.org/880643005/diff/1/pkg/analysis_server/lib/src/...
File pkg/analysis_server/lib/src/analysis_server.dart (right):

https://codereview.chromium.org/880643005/diff/1/pkg/analysis_server/lib/src/...
pkg/analysis_server/lib/src/analysis_server.dart:899: String oldContents =
_overlayState.getContents(source);
There is a subtle bug here that's being carried forward from the existing code.
I hadn't realized that there is a bug until I saw this change, so it's good. The
bug is that two sources representing the same disk file but with different URI's
will not compare equal, so changing the content for one source will not change
the content for the other source. I think we also need to re-write ContentCache
to use the file path rather than the URI, but that would be in a separate CL.

[Paul Berry, 2015-01-26 23:18:29]

On 2015/01/26 23:05:02, Brian Wilkerson wrote:
> LGTM
> 
>
https://codereview.chromium.org/880643005/diff/1/pkg/analysis_server/lib/src/...
> File pkg/analysis_server/lib/src/analysis_server.dart (right):
> 
>
https://codereview.chromium.org/880643005/diff/1/pkg/analysis_server/lib/src/...
> pkg/analysis_server/lib/src/analysis_server.dart:899: String oldContents =
> _overlayState.getContents(source);
> There is a subtle bug here that's being carried forward from the existing
code.
> I hadn't realized that there is a bug until I saw this change, so it's good.
The
> bug is that two sources representing the same disk file but with different
URI's
> will not compare equal, so changing the content for one source will not change
> the content for the other source. I think we also need to re-write
ContentCache
> to use the file path rather than the URI, but that would be in a separate CL.

As discussed in person, we compare and hash FileBasedSource based on path, not
URI, so there actually isn't a bug.  The URI is only used when comparing
elements.  (Phew!)

[Paul Berry, 2015-01-26 23:26:51]

Committed patchset #1 (id:1) manually as 43163 (presubmit successful).