The original implementation of 'testAsync' in mjsunit.js required to
put the call to '%AbortJS' into an 'eval' statement. The reason is that
this call requires the flag --allow-natives-syntax to be set, but the
flag is not set in all mjsunit tests. With the use of 'eval'
compilation errors can be avoided.

The problem with this approach was that the fuzzer started to produce
test cases which include the line 'eval("%AbortJS(message)");', and
this line crashes intentionally. Different to the line
'%Abort(message)', however, the 'eval' statement cannot be filtered
so easily in the fuzzer. Therefore I pulled the implementation of
'testAsync' into a separate file to avoid the 'eval'.

Additional changes: I use '===' now instead of 'deepEquals' in
AsyncAssertion.equals because 'deepEquals' is not available outside
mjsunit.js. Using '===' seems more appropriate anyways because for
all tests but one it is sufficient, and it is more precise than
deepEquals.

R=gsathya@chromium.org

Bug: chromium:774841
Change-Id: I47270aa63ff5a1d6aa76a771f9276eaaf579c5ac
Reviewed-on: https://chromium-review.googlesource.com/1156598Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54833}

It was shipped in Chrome 63.

Bug: v8:5855
Cq-Include-Trybots: luci.v8.try:v8_linux_noi18n_rel_ng
Change-Id: Icc00b8300622d1c7b5662be8ac5e425b9781f666
Reviewed-on: https://chromium-review.googlesource.com/858381
Commit-Queue: Adam Klein <adamk@chromium.org>
Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50558}

Per https://github.com/tc39/proposal-async-iteration/pull/102/files:

AsyncGeneratorResolve no longer unwraps a value component. Instead, the value is
unwrapped before the builtin call via Await, allowing Promise rejections to
affect the generator control flow.

Thus, all `yield <expr>` implicitly become `yield await <expr>`.

Additionally, `return <expr>` becomes `return await <expr>`. Finally, when the
generator is resumed with `.return()`, the parameter passed to .return() is
awaited before generator execution properly continues).

BUG=v8:6187, v8:5855
R=littledan@chromium.org, neis@chromium.org, adamk@chromium.org
TBR=rmcilroy@chromium.org, neis@chromium.org

Cq-Include-Trybots: master.tryserver.v8:v8_linux_noi18n_rel_ng
Change-Id: Id7718028fd555481f9f4ca0dbecfa788e3057c48
Reviewed-on: https://chromium-review.googlesource.com/594500Reviewed-by: Caitlin Potter <caitp@igalia.com>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Caitlin Potter <caitp@igalia.com>
Cr-Commit-Position: refs/heads/master@{#47058}

This reverts commit 409f84c9.

Reason for revert: Breaks nosnap debug:
https://build.chromium.org/p/client.v8/builders/V8%20Linux%20-%20nosnap%20-%20debug/builds/14288

Original change's description:
> [async-iteration] implement spec-change to `yield` in async generators
> 
> Per https://github.com/tc39/proposal-async-iteration/pull/102/files:
> 
> AsyncGeneratorResolve no longer unwraps a value component. Instead, the
> value is unwrapped before the builtin call via Await, allowing Promise
> rejections to affect the generator control flow.
> 
> Thus, all `yield <expr>` implicitly become `yield await <expr>`.
> 
> Additionally, `return <expr>` becomes `return await <expr>`. Finally, when
> the generator is resumed with `.return()`, the parameter passed to .return()
> is awaited before generator execution properly continues).
> 
> BUG=v8:5855
> R=​littledan@chromium.org, neis@chromium.org, adamk@chromium.org
> 
> Cq-Include-Trybots: master.tryserver.v8:v8_linux_noi18n_rel_ng
> Change-Id: Ife084076c3ed434b5467e6aeba14082f8b410ad5
> Reviewed-on: https://chromium-review.googlesource.com/523844
> Commit-Queue: Caitlin Potter <caitp@igalia.com>
> Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
> Reviewed-by: Georg Neis <neis@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#47011}

TBR=rmcilroy@chromium.org,adamk@chromium.org,yangguo@chromium.org,neis@chromium.org,littledan@chromium.org,gsathya@chromium.org,caitp@igalia.com

Change-Id: Ie6ad7e5410a3a89aab7a5dc68de36eb27b9354fe
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:5855
Cq-Include-Trybots: master.tryserver.v8:v8_linux_noi18n_rel_ng
Reviewed-on: https://chromium-review.googlesource.com/593952Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47013}

Per https://github.com/tc39/proposal-async-iteration/pull/102/files:

AsyncGeneratorResolve no longer unwraps a value component. Instead, the
value is unwrapped before the builtin call via Await, allowing Promise
rejections to affect the generator control flow.

Thus, all `yield <expr>` implicitly become `yield await <expr>`.

Additionally, `return <expr>` becomes `return await <expr>`. Finally, when
the generator is resumed with `.return()`, the parameter passed to .return()
is awaited before generator execution properly continues).

BUG=v8:5855
R=littledan@chromium.org, neis@chromium.org, adamk@chromium.org

Cq-Include-Trybots: master.tryserver.v8:v8_linux_noi18n_rel_ng
Change-Id: Ife084076c3ed434b5467e6aeba14082f8b410ad5
Reviewed-on: https://chromium-review.googlesource.com/523844
Commit-Queue: Caitlin Potter <caitp@igalia.com>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47011}