vmservice: Add /coverage collection to scripts, classes and libraries.

Coverage data for single entities can be obtained by querying:
 * script: isolate/id/script/name/coverage
 * class: isolate/id/class/id/coverage
 * library: isolate/id/library/id/coverage

Some numbers (curl on vm service):
 * old base line (full coverage of dart:core + script computing faculty): ~1.2s
 * generation for just the script file: ~12ms
 * generation of dart:core (after executing fac script): ~150ms
 * generation of dart:core-patch/array.dart: ~12ms

BUG=
R=johnmccutchan@google.com

Committed: https://code.google.com/p/dart/source/detail?r=37676

[Cutch, 2014-06-23 16:23:12]

https://codereview.chromium.org/346003003/diff/40001/runtime/vm/coverage.cc
File runtime/vm/coverage.cc (right):

https://codereview.chromium.org/346003003/diff/40001/runtime/vm/coverage.cc#n...
runtime/vm/coverage.cc:253: for (intptr_t i = 0; i < num_scripts; i++) {
Factor this code into a utility method?

FindLibraryWithScriptName(...).

https://codereview.chromium.org/346003003/diff/40001/runtime/vm/coverage.cc#n...
runtime/vm/coverage.cc:263: ClassDictionaryIterator it(lib,
ClassDictionaryIterator::kIteratePrivate);
Just call PrintJSONForLibrary instead of duplicating the code?

https://codereview.chromium.org/346003003/diff/40001/runtime/vm/service_test.cc
File runtime/vm/service_test.cc (right):

https://codereview.chromium.org/346003003/diff/40001/runtime/vm/service_test....
runtime/vm/service_test.cc:1271:
"\"name\":\"test-lib\",\"user_name\":\"test-lib\","
The result of all of these requests is the same. Could you construct tests which
check for the reduced output?

[Michael Lippautz (Google), 2014-06-24 17:51:07]

PTAL

https://codereview.chromium.org/346003003/diff/40001/runtime/vm/coverage.cc
File runtime/vm/coverage.cc (right):

https://codereview.chromium.org/346003003/diff/40001/runtime/vm/coverage.cc#n...
runtime/vm/coverage.cc:253: for (intptr_t i = 0; i < num_scripts; i++) {
On 2014/06/23 16:23:11, Cutch wrote:
> Factor this code into a utility method?
> 
> FindLibraryWithScriptName(...).

Done.

Added
  static RawScript* Script::FindByUrl(...)
  RawLibrary* Script::FindLibrary()

https://codereview.chromium.org/346003003/diff/40001/runtime/vm/coverage.cc#n...
runtime/vm/coverage.cc:263: ClassDictionaryIterator it(lib,
ClassDictionaryIterator::kIteratePrivate);
On 2014/06/23 16:23:11, Cutch wrote:
> Just call PrintJSONForLibrary instead of duplicating the code?

Done.

https://codereview.chromium.org/346003003/diff/40001/runtime/vm/service_test.cc
File runtime/vm/service_test.cc (right):

https://codereview.chromium.org/346003003/diff/40001/runtime/vm/service_test....
runtime/vm/service_test.cc:1271:
"\"name\":\"test-lib\",\"user_name\":\"test-lib\","
On 2014/06/23 16:23:11, Cutch wrote:
> The result of all of these requests is the same. Could you construct tests
which
> check for the reduced output?

The class coverage test now checks against an actual class.

[Cutch, 2014-06-24 18:49:19]

lgtm

[Michael Lippautz (Google), 2014-06-25 00:06:59]

Committed patchset #3 manually as r37676 (presubmit successful).

[Ivan Posva, 2014-06-26 10:14:33]

Michael, John,

There is a general problem with the assumption that a script has only been
loaded into a single library. We might need to change the encoding of how
scripts are being accessed in general.

Also please update the API so that the implementation detail of script filters
does not leak out into the public API.

Thanks,
-Ivan

https://codereview.chromium.org/346003003/diff/100001/runtime/vm/object.cc
File runtime/vm/object.cc (right):

https://codereview.chromium.org/346003003/diff/100001/runtime/vm/object.cc#ne...
runtime/vm/object.cc:8325: return lib.raw();
How does this work for scripts that have been included in multiple libraries?

https://codereview.chromium.org/346003003/diff/100001/runtime/vm/service.cc
File runtime/vm/service.cc (right):

https://codereview.chromium.org/346003003/diff/100001/runtime/vm/service.cc#n...
runtime/vm/service.cc:1293: CodeCoverage::PrintJSONForLibrary(lib,
Script::Handle(), js);
I find this an awkward API. If you want to factor out the coverage printing for
a library with a script filter within the CodeCoverage class, then please make
it a private implementation method instead of leaking out the functionality to
the public API.