gin: Make it possible to use gin array buffers when running on top of blink

gin: Make it possible to use gin array buffers when running on top of blink

This approach won't let use share an array buffer with blink, however,
it's good enough for a mojo js app.

For gin::Wrappable objects that want to interact with blink APIs, they
need to provide a custom converter to and from WebArrayBuffer(View)

BUG=none
R=abarth@chromium.org, dslomov@chromium.org, sky@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=252190

[Dmitry Lomov (no reviews), 2014-02-19 12:27:36]

lgtm

[abarth-chromium, 2014-02-19 15:52:55]

LGTM

https://codereview.chromium.org/172133002/diff/1/gin/array_buffer.cc
File gin/array_buffer.cc (right):

https://codereview.chromium.org/172133002/diff/1/gin/array_buffer.cc#newcode85
gin/array_buffer.cc:85:
array->GetAlignedPointerFromInternalField(kBufferViewPrivateIndex)));
This CL is a good step, but I think you still get in trouble on this line.  How
do we know that this static_cast is safe?  If the ArrayBuffer is external
because Blink has made it external, this fields might not point to a
ArrayBuffer::Private...

[jochen (gone - plz use gerrit), 2014-02-19 16:04:53]

PTAL

[jochen (gone - plz use gerrit), 2014-02-19 16:49:43]

I install a WrapperInfo in the correct slot now (blink already does this), so we
can check that the correct implementation handles the array buffer. (also
updated the blink side cl to add the check)

[abarth-chromium, 2014-02-19 18:59:57]

LGTM

https://codereview.chromium.org/172133002/diff/160001/gin/array_buffer.cc
File gin/array_buffer.cc (right):

https://codereview.chromium.org/172133002/diff/160001/gin/array_buffer.cc#new...
gin/array_buffer.cc:91: << "Cannot mix blink and gin ArrayBuffers";
CHECK_EQ ?

This kind of sucks, but it seems ok in the near term.

[jochen (gone - plz use gerrit), 2014-02-19 20:22:13]

The CQ bit was checked by jochen@chromium.org

[commit-bot: I haz the power, 2014-02-19 20:26:38]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/jochen@chromium.org/172133002/240001

[commit-bot: I haz the power, 2014-02-20 00:23:51]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/jochen@chromium.org/172133002/240001

[commit-bot: I haz the power, 2014-02-20 03:08:12]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/jochen@chromium.org/172133002/240001

[commit-bot: I haz the power, 2014-02-20 05:23:48]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/jochen@chromium.org/172133002/240001

[jochen (gone - plz use gerrit), 2014-02-20 08:24:08]

Committed patchset #5 manually as r252190 (presubmit successful).