deps: update V8 to 5.1.281.69

[targos]

Checklist

• tests and code linting passes
• the commit message follows commit guidelines

Affected core subsystem(s)

v8

Description of change

V8 5.1 is out with stable Chrome so here is the PR to update our copy!
I picked up the latest commit from the 5.1-lkgr branch, applied all (I hope) relevant floating patches and the commits from our vee-eight-5.1 branch.

cc @nodejs/v8, @nodejs/post-mortem

CI: https://ci.nodejs.org/job/node-test-pull-request/2817/

[targos]

@mhdawson would you like me to try a revert of 0899ea7 and 2d524bc ?

[targos]

FYI here is the list of V8 API changes in 5.1:

• Add memory pressure notification API: CL
• Introduce v8::MicrotasksScope: CL
• Use a different GCCallbackFlag for GCs triggered by CollectAllAvailableGarbage: CL
• MicrotasksCompletedCallback: CL
• Clarify the limits of ResourceConstraints: CL

Source: https://docs.google.com/document/d/1g8JFi8T_oAE_7uAri7Njtig7fKaPDfotU6huOa1alds

Edit: I guess these make the update semver-major ?

[ronkorving]

Did any of those APIs actually change or are they just new APIs? (seems like at least mostly they're just new..)

[bnoordhuis]

@targos Did you check whether it's possible to drop the deps/v8 include from node.gyp now? I mean this one:

diff --git a/node.gyp b/node.gyp
index 0d32905..4187ce6 100644
--- a/node.gyp
+++ b/node.gyp
@@ -117,7 +117,6 @@
         'tools/msvs/genfiles',
         'deps/uv/src/ares',
         '<(SHARED_INTERMEDIATE_DIR)', # for node_natives.h
-        'deps/v8' # include/v8_platform.h
       ],

       'sources': [

@ronkorving Yes, they're mostly additive. It's not a drop-in replacement, though.

[mhdawson]

@targos if its easy for you that would be useful, but otherwise I'm happy to test after the upgrade islanded and remove if appropriate.

[ofrobots]

I think we should add ofrobots#23 (once we have thumbs up from the V8 team).

There are no breaking API changes between 5.0 and 5.1, there were some ABI differences. @matthewloring has been working on bridging that ABI gap. This would make V8 5.1 a semver-minor as opposed to a semver-major, and enable us to get this landed into Node 6.x.

I think we should wait for ofrobots#23 is reviewed, and add it here before landing this PR.

[targos]

Nice, let's wait for it then.

[targos]

New CI with the change from @bnoordhuis : https://ci.nodejs.org/job/node-test-pull-request/2822/
V8 tests run: https://ci.nodejs.org/job/node-test-commit-v8-linux/105/

[ofrobots]

For the first commit (4f0c3be317b0b5ad1ea12306409671d9be53b762) I would prefer if the floating backports were refloated rather than squashing. That makes it easier to audit what changes from upstream we are floating on Node.js side.
EDIT: typo.

[targos]

OK. I will make the change.

[targos]

@ofrobots done

[auguradmin]

@targos What's the plan on merging v8 5.1.x with master? As I'm sure you're aware, it has a new garbage collector ( Orinoco ) that should speed node up dramatically and reduce memory. Can you share anything?

[Fishrock123]

Is this able to land in v6 or not?

[ofrobots]

@Fishrock123 That's the objective behind ofrobots#23. Once / If we are able to get sign-off from the V8 team and @nodejs/v8, we could add that commit to this PR. That would make this PR a semver-minor, and hence landable on v6.x.

[rvagg]

@ofrobots it looks like there might be some challenges over at the ABI compatibility changes being proposed. In the event that we're unable to make enough compromise we should start a discussion about a possible floating patch, although I think it would need to be pretty minimal to be palatable here. Ideal is to do this all upstream of course, just keep us in the loop so there's enough brew-time for decision making on this because it's such a new way of thinking about our major release lines.

[ofrobots]

@rvagg This indeed a new way of thinking about major releases, and I am definitely interested in careful vetting of the ABI compatibility patch. The patch (ofrobots#23) is looking pretty small at the moment.

Note that I don't expect the patch to land upstream in V8 5.1 – this is not a bugfix, and will have no coverage from Chrome canaries to qualify it to land upstream in V8 5.1 branch.

The only reason @matthewloring has been putting energy into this for the benefit of Node.js. We're happy to do the work to make it possible for V8 5.1 to be landable in Node.js w/ ABI compatibility with V8 5.0. It is independent decision on whether the patch looks reasonable enough to land that should probably be made by the @nodejs/v8 or the CTC after careful evaluation/brew time.

The benefit of course is that V8 5.1 brings-in almost all of ES6 along with performance improvements.

[ofrobots]

@targos For 2d2d6ca, I normally squash that commit with the previous two, but it is okay to keep it unsquashed too. If you chose the latter option, can you truncate the commit abstract to fit the 50 char limit?

[rvagg]

👍 thanks for the hardwork @ofrobots, @matthewloring and others. This shift is something we've not communicated to the public very well and will be a surprise for a lot of people. I'm planning on doing some writing ASAP to start the messaging about the change in policy.

[targos]

I normally squash that commit with the previous two, but it is okay to keep it unsquashed too.

I will squash them when I land the PR

[ofrobots]

Backport to v6.x: #8054