WIP: Fix WebIDL spec violation: prototype names end with "Prototype".

WIP: Fix WebIDL spec violation: prototype names end with "Prototype".

Unfortunately, this can't land (DO NOT SUBMIT) because it breaks the
garbage collection due to an outstanding issue that was noted in a TODO.

Adds the word "Prototype" to the end of all prototype names, and also
explicitly sets the name of the instances *without* the word "Prototype"
(otherwise they would get the word "Prototype" too). Setting the name of
the instance breaks GC for reasons I don't understand.

This is required by
https://heycam.github.io/webidl/#interface-prototype-object and checked
by idlharness tests.

BUG=687431

[Matt Giuca, 2017-02-01 02:48:06]

mgiuca@chromium.org changed reviewers:
+ yukishiino@chromium.org

[Matt Giuca, 2017-02-01 02:48:07]

yukishiino: Please have a look at this (WIP) CL. Feel free to take it over (I
don't understand this stuff and I don't really intend to work on it, but it may
be useful to you).

[haraken, 2017-02-01 03:57:12]

haraken@chromium.org changed reviewers:
+ haraken@chromium.org

[haraken, 2017-02-01 03:57:12]

https://codereview.chromium.org/2666943003/diff/1/third_party/WebKit/Source/b...
File third_party/WebKit/Source/bindings/core/v8/V8DOMConfiguration.cpp (right):

https://codereview.chromium.org/2666943003/diff/1/third_party/WebKit/Source/b...
third_party/WebKit/Source/bindings/core/v8/V8DOMConfiguration.cpp:622: //
fast/dom/minor-dom-gc.html fails if we set the class string).

yukishiino@: Is this still true? We've made a lot of changes to the minor GC
algorithm, so we might want to check if that is still a problem or not.

[Matt Giuca, 2017-02-01 03:59:47]

https://codereview.chromium.org/2666943003/diff/1/third_party/WebKit/Source/b...
File third_party/WebKit/Source/bindings/core/v8/V8DOMConfiguration.cpp (right):

https://codereview.chromium.org/2666943003/diff/1/third_party/WebKit/Source/b...
third_party/WebKit/Source/bindings/core/v8/V8DOMConfiguration.cpp:622: //
fast/dom/minor-dom-gc.html fails if we set the class string).
On 2017/02/01 03:57:12, haraken wrote:
> 
> yukishiino@: Is this still true? We've made a lot of changes to the minor GC
> algorithm, so we might want to check if that is still a problem or not.
> 

I just tried it and it fails under this CL.

[Yuki, 2017-02-02 13:05:51]

yukishiino@chromium.org changed reviewers:
+ jochen@chromium.org

[Yuki, 2017-02-02 13:05:51]

+jochen@

Before this CL, a div element has no own property.
  Object.getOwnPropertyNames(div)
  => []  // empty array
  Object.getOwnPropertySymbols(div)
  => []  // empty array

After this CL, a div element has an own property.
  Object.getOwnPropertySymbols(div)
  => [Symbol(Symbol.toStringTag)]

I guess that this own property prevents V8's minor GC to collect the div
element.

jochen@, is it right that V8's minor GC does not collect an object that has an
own property?  Or, what is the exact restrictions of minor GC?

[jochen (gone - plz use gerrit), 2017-02-03 06:29:43]

jochen@chromium.org changed reviewers:
+ mlippautz@chromium.org

[jochen (gone - plz use gerrit), 2017-02-03 06:29:43]

the restriction is that the object must be unchanged. I guess that setting the
property results in a map transition and the object can no longer be collected.

[Yuki, 2017-02-03 06:34:03]

On 2017/02/03 06:29:43, jochen (travelling til Feb 4) wrote:
> the restriction is that the object must be unchanged. I guess that setting the
> property results in a map transition and the object can no longer be
collected.

Thanks for the answer.  It makes sense.

I'll update the comment accordingly.  Because we're not going to add
per-instance class string so far, this restriction is okay, I think.

[Matt Giuca, 2017-02-06 00:06:45]

Description was changed from

==========
WIP: Fix WebIDL spec violation: prototype names end with "Prototype".

Unfortunately, this can't land (DO NOT SUBMIT) because it breaks the
garbage collection due to an outstanding issue that was noted in a TODO.

Adds the word "Prototype" to the end of all prototype names, and also
explicitly sets the name of the instances *without* the word "Prototype"
(otherwise they would get the word "Prototype" too). Setting the name of
the instance breaks GC for reasons I don't understand.

This is required by
https://heycam.github.io/webidl/#interface-prototype-object and checked
by idlharness tests.

BUG=687431
==========

to

==========
WIP: Fix WebIDL spec violation: prototype names end with "Prototype".

Unfortunately, this can't land (DO NOT SUBMIT) because it breaks the
garbage collection due to an outstanding issue that was noted in a TODO.

Adds the word "Prototype" to the end of all prototype names, and also
explicitly sets the name of the instances *without* the word "Prototype"
(otherwise they would get the word "Prototype" too). Setting the name of
the instance breaks GC for reasons I don't understand.

This is required by
https://heycam.github.io/webidl/#interface-prototype-object and checked
by idlharness tests.

BUG=687431
==========

[Matt Giuca, 2017-02-06 00:07:18]

OK looks like this can be closed now.

Yuki's comment change CL:
https://codereview.chromium.org/2669263004/