Should we really be calling the serialized script value logic when getting elements out of Lists re…

Should we really be calling the serialized script value logic when getting elements out of Lists returned by dartium? I sure hope not as that is blowing up some multiple dom isolate cases. If there are cases in the dom that require the serialized script value conversions for array elements we can add it in we just need to fix the code so we stop returning null when we shouldn't be.

BUG=
R=alanknight@google.com

Committed: https://github.com/dart-lang/sdk/commit/761a8151ce9b3798b888b4ad86ac5997d1bdf09e

[Jacob, 2015-11-06 18:53:08]

jacobr@google.com changed reviewers:
+ alanknight@google.com, terry@google.com

[Jacob, 2015-11-06 18:53:09]

This change scares me a bit. Please take time reviewing it. I'm not sure what
the correct approach is.

[Alan Knight, 2015-11-09 20:46:07]

https://codereview.chromium.org/1421023005/diff/1/sdk/lib/html/html_common/co...
File sdk/lib/html/html_common/conversions_dartium.dart (right):

https://codereview.chromium.org/1421023005/diff/1/sdk/lib/html/html_common/co...
sdk/lib/html/html_common/conversions_dartium.dart:245: // classes.
I think the largest issue here is that we call wrap_jso without any information
about context. So all we know is that we have some object, not where it's coming
from or what the expected conversion is. Dart2js has better support for this,
and I added some of their code for dealing with input parameters when calling
JS, where this happens more often. So far we haven't had a pressing need to do
it for return values/callback parameters, but it's definitely something we ought
to do.

https://codereview.chromium.org/1421023005/diff/1/sdk/lib/html/html_common/co...
sdk/lib/html/html_common/conversions_dartium.dart:390: operator [](int index) =>
wrap_jso_no_SerializedScriptvalue(js.JsNative.getArrayIndex(blink_jsObject,
index));
I *think* this might be ok, but should look at the uses more carefully. But
basically if we did a wrap_jso to get here, then if we ought to be treating
something as a serialized script value it would be the whole list, not each item
individually. And since structured clone is trying to preserve identity,
re-cloning each list element might give incorrect answers.

And trying to do structured clone on every value probably doesn't help our perf.

[Alan Knight, 2015-11-11 23:16:22]

Let's give it a try and see if anything breaks. LGTM.

[Jacob, 2015-11-11 23:19:16]

Committed patchset #1 (id:1) manually as
761a8151ce9b3798b888b4ad86ac5997d1bdf09e (presubmit successful).