Generate less code when importing dart:mirrors.

Generate less code when importing dart:mirrors.

BUG=http://dartbug.com/11340
BUG=http://dartbug.com/11218
R=johnniwinther@google.com, kasperl@google.com

Committed: https://code.google.com/p/dart/source/detail?r=24453

[ahe, 2013-06-19 20:52:36]

This fixes 11218 (JS-interop example produces > 670kb .js file), and it turns
out that it also fixes the crash in 11340.

I'm not sure what the problem in 11340 is, and it might crop up again.  This CL
fixes the problem by not trying to retain metadata unless it is needed.

[kasperl, 2013-06-20 07:16:46]

LGTM. Is there any way we can test this?

https://codereview.chromium.org/17315012/diff/4001/dart/sdk/lib/_internal/com...
File dart/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
(right):

https://codereview.chromium.org/17315012/diff/4001/dart/sdk/lib/_internal/com...
dart/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart:164: bool
retainedMetadata = false;
Add a comment that explains the difference between the two 'retain' flags? Maybe
rename retainedMetadata to hasRetainedMetadata?

[Johnni Winther, 2013-06-20 10:17:02]

lgtm

https://codereview.chromium.org/17315012/diff/4001/dart/sdk/lib/_internal/com...
File dart/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
(right):

https://codereview.chromium.org/17315012/diff/4001/dart/sdk/lib/_internal/com...
dart/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart:170:
final List<List> metadataInstantiatedClasses = <List>[];
Add a comment of what the content of the list of lists are. As far I can see its
a list of [Element,TreeElements] pairs.

[ahe, 2013-06-21 12:24:39]

I've extended mirror_tree_shaking_test.dart to test that metadata isn't
retained.  I'll create a separate CL to test http://dartbug.com/11340.

https://codereview.chromium.org/17315012/diff/4001/dart/sdk/lib/_internal/com...
File dart/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
(right):

https://codereview.chromium.org/17315012/diff/4001/dart/sdk/lib/_internal/com...
dart/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart:164: bool
retainedMetadata = false;
On 2013/06/20 07:16:46, kasperl wrote:
> Add a comment that explains the difference between the two 'retain' flags?
Maybe
> rename retainedMetadata to hasRetainedMetadata?

Done.

https://codereview.chromium.org/17315012/diff/4001/dart/sdk/lib/_internal/com...
dart/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart:170:
final List<List> metadataInstantiatedClasses = <List>[];
On 2013/06/20 10:17:02, Johnni Winther wrote:
> Add a comment of what the content of the list of lists are. As far I can see
its
> a list of [Element,TreeElements] pairs.

I added a class to represent this concept, a dependency.

[ahe, 2013-06-26 07:10:08]

Committed patchset #3 manually as r24453 (presubmit successful).