Timing hooks to profile linters (#24548).

Timing hooks to profile linters (#24548).

Adds a `TimedAstVisitor` that wraps and times base visitors.  The perf hit for collecting timing was neglible so I opted to NOT surface a way to not collect the data.  We can add that if needed.

Once this is published in a new analyzer, I can bake client support into (for example) the linter.

More context and a client mock here: https://github.com/dart-lang/sdk/issues/24548


BUG=
R=brianwilkerson@google.com

Committed: https://github.com/dart-lang/sdk/commit/9a042501c945db0b6a40f89983b7dd22f4266278

[pquitslund, 2016-03-15 22:43:05]

Description was changed from

==========
Timing hooks to profile linters (#24548).

Adds a `TimedAstVisitor` that wraps and times base visitors.  The perf hit for
collecting timing was neglibible so I opted to NOT surface a way to not collect
the data.  We can add that if needed.

Once this is published in a new analyzer, I can bake client support into (for
example) the linter.

As a teaser, here's what a first cut at a perf summary using this data looks
like:

```
29 files analyzed, 73 issues found, in 4603 ms.
-----------------------------------------------
always_declare_return_types                          65
avoid_as                                                              1
camel_case_types                                              7
-----------------------------------------------

-----------------------------------------------
Timings                                                            ms
-----------------------------------------------
always_declare_return_types                            5
avoid_as                                                              2
camel_case_types                                            14
-----------------------------------------------
Total                                                                  21
-----------------------------------------------
```

BUG=
==========

to

==========
Timing hooks to profile linters (#24548).

Adds a `TimedAstVisitor` that wraps and times base visitors.  The perf hit for
collecting timing was neglible so I opted to NOT surface a way to not collect
the data.  We can add that if needed.

Once this is published in a new analyzer, I can bake client support into (for
example) the linter.

More context and a client mock here:
https://github.com/dart-lang/sdk/issues/24548


BUG=
==========

[pquitslund, 2016-03-15 22:43:05]

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

[Brian Wilkerson, 2016-03-15 22:57:24]

Other than the recursive call to visitChildren, LGTM.

https://codereview.chromium.org/1807723002/diff/1/pkg/analyzer/lib/dart/ast/v...
File pkg/analyzer/lib/dart/ast/visitor.dart (right):

https://codereview.chromium.org/1807723002/diff/1/pkg/analyzer/lib/dart/ast/v...
pkg/analyzer/lib/dart/ast/visitor.dart:916: : stopwatch = watch != null ? watch
: new Stopwatch();
or "watch ?? new Stopwatch()"

https://codereview.chromium.org/1807723002/diff/1/pkg/analyzer/lib/dart/ast/v...
pkg/analyzer/lib/dart/ast/visitor.dart:923: node.visitChildren(this);
I don't think we want the calls to visitChildren. In the linter case that would
cause nodes to be visited an exponential number of times.

https://codereview.chromium.org/1807723002/diff/1/pkg/analyzer/lib/src/servic...
File pkg/analyzer/lib/src/services/lint.dart (right):

https://codereview.chromium.org/1807723002/diff/1/pkg/analyzer/lib/src/servic...
pkg/analyzer/lib/src/services/lint.dart:59: Stopwatch stopwatch =
timers[linter.name];
Or you could use putIfAbsent.

[pquitslund, 2016-03-15 23:09:17]

Thanks!

https://codereview.chromium.org/1807723002/diff/1/pkg/analyzer/lib/dart/ast/v...
File pkg/analyzer/lib/dart/ast/visitor.dart (right):

https://codereview.chromium.org/1807723002/diff/1/pkg/analyzer/lib/dart/ast/v...
pkg/analyzer/lib/dart/ast/visitor.dart:916: : stopwatch = watch != null ? watch
: new Stopwatch();
On 2016/03/15 22:57:24, Brian Wilkerson wrote:
> or "watch ?? new Stopwatch()"

Done.

https://codereview.chromium.org/1807723002/diff/1/pkg/analyzer/lib/dart/ast/v...
pkg/analyzer/lib/dart/ast/visitor.dart:923: node.visitChildren(this);
On 2016/03/15 22:57:24, Brian Wilkerson wrote:
> I don't think we want the calls to visitChildren. In the linter case that
would
> cause nodes to be visited an exponential number of times.

Ah, yes!  Fixed.

https://codereview.chromium.org/1807723002/diff/1/pkg/analyzer/lib/src/servic...
File pkg/analyzer/lib/src/services/lint.dart (right):

https://codereview.chromium.org/1807723002/diff/1/pkg/analyzer/lib/src/servic...
pkg/analyzer/lib/src/services/lint.dart:59: Stopwatch stopwatch =
timers[linter.name];
On 2016/03/15 22:57:24, Brian Wilkerson wrote:
> Or you could use putIfAbsent.

Good call.  Keep forgetting that one!

[pquitslund, 2016-03-15 23:10:43]

Description was changed from

==========
Timing hooks to profile linters (#24548).

Adds a `TimedAstVisitor` that wraps and times base visitors.  The perf hit for
collecting timing was neglible so I opted to NOT surface a way to not collect
the data.  We can add that if needed.

Once this is published in a new analyzer, I can bake client support into (for
example) the linter.

More context and a client mock here:
https://github.com/dart-lang/sdk/issues/24548


BUG=
==========

to

==========
Timing hooks to profile linters (#24548).

Adds a `TimedAstVisitor` that wraps and times base visitors.  The perf hit for
collecting timing was neglible so I opted to NOT surface a way to not collect
the data.  We can add that if needed.

Once this is published in a new analyzer, I can bake client support into (for
example) the linter.

More context and a client mock here:
https://github.com/dart-lang/sdk/issues/24548


BUG=
R=brianwilkerson@google.com

Committed:
https://github.com/dart-lang/sdk/commit/9a042501c945db0b6a40f89983b7dd22f4266278
==========

[pquitslund, 2016-03-15 23:10:45]

Committed patchset #1 (id:1) manually as
9a042501c945db0b6a40f89983b7dd22f4266278 (presubmit successful).