Dont install methods if implementation superclass corresponds to an installed extension class

Dont install methods if implementation superclass corresponds to an installed extension class

BUG=
R=leafp@google.com

Committed: https://github.com/dart-lang/dev_compiler/commit/a637e4102fff7d32760bd800971c7645309f5855

[sra1, 2016-05-14 22:17:42]

sra@google.com changed reviewers:
+ jmesserly@google.com, leafp@google.com, vsm@google.com

[sra1, 2016-05-14 22:17:43]

This is a hacky experiment.
I'm not sure if this is actually correct. html tests pass, but I'm not sure how
good the non-fail test coverage is.

It reduces the number of prototype-prototype copies from ~2000 to ~700 (for ~400
classes).
Our app load time goes from 3.9s to 3.3s.

It is reliant on superclasses being installed before subclasses.
Is this something that is already in place?

[sra1, 2016-05-14 22:34:46]

On 2016/05/14 22:17:43, sra1 wrote:
> This is a hacky experiment.
> I'm not sure if this is actually correct. html tests pass, but I'm not sure
how
> good the non-fail test coverage is.
> 
> It reduces the number of prototype-prototype copies from ~2000 to ~700 (for
~400
> classes).
> Our app load time goes from 3.9s to 3.3s.

This is all in loading the dart_sdk, which goes from 1.15s to 0.62s.
This is where we would expect it to show up.

> 
> It is reliant on superclasses being installed before subclasses.
> Is this something that is already in place?

[Leaf, 2016-05-16 18:03:07]

lgtm

https://codereview.chromium.org/1979863002/diff/1/tool/input_sdk/private/ddc_...
File tool/input_sdk/private/ddc_runtime/classes.dart (right):

https://codereview.chromium.org/1979863002/diff/1/tool/input_sdk/private/ddc_...
tool/input_sdk/private/ddc_runtime/classes.dart:321: if(JS('bool',
'#.__proto__._xxx !== #', jsProto, extParent)) {
Maybe use a symbol to be more robust?  Or maybe just a better obfuscated name
(e.g. __ddc_extension_prototype or something)?

[sra1, 2016-05-16 22:03:57]

Description was changed from

==========
Dont install methods if implementation superclass corresponds to an installed
extension class

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

to

==========
Dont install methods if implementation superclass corresponds to an installed
extension class

BUG=
R=leafp@google.com

Committed:
https://github.com/dart-lang/dev_compiler/commit/a637e4102fff7d32760bd800971c...
==========

[sra1, 2016-05-16 22:03:59]

Committed patchset #2 (id:20001) manually as
a637e4102fff7d32760bd800971c7645309f5855 (presubmit successful).

[Jennifer Messerly, 2016-05-17 17:50:51]

https://codereview.chromium.org/1979863002/diff/20001/tool/input_sdk/private/...
File tool/input_sdk/private/ddc_runtime/classes.dart (right):

https://codereview.chromium.org/1979863002/diff/20001/tool/input_sdk/private/...
tool/input_sdk/private/ddc_runtime/classes.dart:286: final _installedDartPeers =
JS('', 'new Map()');
isn't this identical to _extensionType field?

See below line 348:

// Mark the JS type's instances so we can easily check for extensions.
jsProto[$_extensionType] = $dartExtType;
$_installProperties(jsProto, extProto);

then below we set key: jsProto value: extProto in the Map.