DevTools: Make eslint mandatory and check node.js/npm modules in presubmit

DevTools: Make eslint mandatory and check node.js/npm modules in presubmit

- Adds presubmit step to ensure users are running on node.js v4 or later
and installs node_modules using 'npm install'. If 'npm install' fails
(e.g. npm registry has an outage), it's a soft warning that doesn't fail
the presubmit check. Most likely, the user already has node_modules installed.

- Automatically installs local node.js for Linux users; Windows and Mac users
have official node.js installers

- Even though this runs 'npm install' with every presubmit, if it has been
installed once, running 'npm install' is a quick check (<1 sec to run)

- Makes eslint a mandatory presubmit step (before if it wasn't installed,
it would skip the step with a soft warning).

BUG=642046
Committed: https://crrev.com/6d7f23b089bcfd951446564995916395b579140d
Cr-Commit-Position: refs/heads/master@{#425777}

[chenwilliam, 2016-09-13 21:50:34]

Description was changed from

==========
DevTools: Make eslint mandatory and check node.js/npm modules in presubmit

- Adds presubmit step to ensure users are running on node.js v4 or later
and installs node_modules using 'npm install'. If 'npm install' fails
(e.g. npm registry has an outage), it's a soft warning that doesn't fail
the presubmit check.
- Makes eslint a mandatory presubmit step (before if it wasn't installed,
it would skip the step with a soft warning).

BUG=642046
==========

to

==========
DevTools: Make eslint mandatory and check node.js/npm modules in presubmit

- Adds presubmit step to ensure users are running on node.js v4 or later
and installs node_modules using 'npm install'. If 'npm install' fails
(e.g. npm registry has an outage), it's a soft warning that doesn't fail
the presubmit check. Most likely, the users already has node_modules installed.
  - Even though this runs 'npm install' with every presubmit, once eslint
  has been installed once, running 'npm install' is a quick check (<1 sec to
run)
- Makes eslint a mandatory presubmit step (before if it wasn't installed,
it would skip the step with a soft warning).

BUG=642046
==========

[chenwilliam, 2016-09-13 21:50:34]

chenwilliam@chromium.org changed reviewers:
+ dgozman@chromium.org

[chenwilliam, 2016-09-13 21:51:24]

Description was changed from

==========
DevTools: Make eslint mandatory and check node.js/npm modules in presubmit

- Adds presubmit step to ensure users are running on node.js v4 or later
and installs node_modules using 'npm install'. If 'npm install' fails
(e.g. npm registry has an outage), it's a soft warning that doesn't fail
the presubmit check. Most likely, the users already has node_modules installed.
  - Even though this runs 'npm install' with every presubmit, once eslint
  has been installed once, running 'npm install' is a quick check (<1 sec to
run)
- Makes eslint a mandatory presubmit step (before if it wasn't installed,
it would skip the step with a soft warning).

BUG=642046
==========

to

==========
DevTools: Make eslint mandatory and check node.js/npm modules in presubmit

- Adds presubmit step to ensure users are running on node.js v4 or later
and installs node_modules using 'npm install'. If 'npm install' fails
(e.g. npm registry has an outage), it's a soft warning that doesn't fail
the presubmit check. Most likely, the user already has node_modules installed.
  - Even though this runs 'npm install' with every presubmit, once eslint
  has been installed once, running 'npm install' is a quick check (<1 sec to
run)
- Makes eslint a mandatory presubmit step (before if it wasn't installed,
it would skip the step with a soft warning).

BUG=642046
==========

[chenwilliam, 2016-09-13 21:51:38]

PTAL.

[chenwilliam, 2016-09-14 01:20:27]

Fixed copyright year.

[dgozman, 2016-09-14 16:37:41]

dgozman@chromium.org changed reviewers:
+ lushnikov@chromium.org

[dgozman, 2016-09-14 16:37:42]

+lushnikov

https://codereview.chromium.org/2338753003/diff/20001/third_party/WebKit/Sour...
File third_party/WebKit/Source/devtools/scripts/lint_javascript.py (right):

https://codereview.chromium.org/2338753003/diff/20001/third_party/WebKit/Sour...
third_party/WebKit/Source/devtools/scripts/lint_javascript.py:58: print("!!
NOTE: Javascript linting is mandatory")
Replace this with "Failed to run eslint, run ./scripts/node.py to install
eslint"

https://codereview.chromium.org/2338753003/diff/20001/third_party/WebKit/Sour...
File third_party/WebKit/Source/devtools/scripts/node.py (right):

https://codereview.chromium.org/2338753003/diff/20001/third_party/WebKit/Sour...
third_party/WebKit/Source/devtools/scripts/node.py:8: Ensure node.js and npm
modules are installed
Let's rename this to install_node_deps

[chenwilliam, 2016-09-15 00:40:11]

PTAL.

https://codereview.chromium.org/2338753003/diff/20001/third_party/WebKit/Sour...
File third_party/WebKit/Source/devtools/scripts/lint_javascript.py (right):

https://codereview.chromium.org/2338753003/diff/20001/third_party/WebKit/Sour...
third_party/WebKit/Source/devtools/scripts/lint_javascript.py:58: print("!!
NOTE: Javascript linting is mandatory")
On 2016/09/14 16:37:41, dgozman wrote:
> Replace this with "Failed to run eslint, run ./scripts/node.py to install
> eslint"

Done.

https://codereview.chromium.org/2338753003/diff/20001/third_party/WebKit/Sour...
File third_party/WebKit/Source/devtools/scripts/node.py (right):

https://codereview.chromium.org/2338753003/diff/20001/third_party/WebKit/Sour...
third_party/WebKit/Source/devtools/scripts/node.py:8: Ensure node.js and npm
modules are installed
On 2016/09/14 16:37:41, dgozman wrote:
> Let's rename this to install_node_deps

Done.

[chenwilliam, 2016-09-23 21:51:53]

Patchset #4 (id:60001) has been deleted

[chenwilliam, 2016-09-23 22:03:10]

Patchset #4 (id:80001) has been deleted

[chenwilliam, 2016-09-23 22:04:18]

Description was changed from

==========
DevTools: Make eslint mandatory and check node.js/npm modules in presubmit

- Adds presubmit step to ensure users are running on node.js v4 or later
and installs node_modules using 'npm install'. If 'npm install' fails
(e.g. npm registry has an outage), it's a soft warning that doesn't fail
the presubmit check. Most likely, the user already has node_modules installed.
  - Even though this runs 'npm install' with every presubmit, once eslint
  has been installed once, running 'npm install' is a quick check (<1 sec to
run)
- Makes eslint a mandatory presubmit step (before if it wasn't installed,
it would skip the step with a soft warning).

BUG=642046
==========

to

==========
DevTools: Make eslint mandatory and check node.js/npm modules in presubmit

- Adds presubmit step to ensure users are running on node.js v4 or later
and installs node_modules using 'npm install'. If 'npm install' fails
(e.g. npm registry has an outage), it's a soft warning that doesn't fail
the presubmit check. Most likely, the user already has node_modules installed.
  - Automatically installs local node.js for Linux users; 
  Windows and Mac users have official node.js installers
  - Even though this runs 'npm install' with every presubmit, once eslint
  has been installed once, running 'npm install' is a quick check (<1 sec to
run)
- Makes eslint a mandatory presubmit step (before if it wasn't installed,
it would skip the step with a soft warning).

BUG=642046
==========

[chenwilliam, 2016-09-23 22:05:18]

Description was changed from

==========
DevTools: Make eslint mandatory and check node.js/npm modules in presubmit

- Adds presubmit step to ensure users are running on node.js v4 or later
and installs node_modules using 'npm install'. If 'npm install' fails
(e.g. npm registry has an outage), it's a soft warning that doesn't fail
the presubmit check. Most likely, the user already has node_modules installed.
  - Automatically installs local node.js for Linux users; 
  Windows and Mac users have official node.js installers
  - Even though this runs 'npm install' with every presubmit, once eslint
  has been installed once, running 'npm install' is a quick check (<1 sec to
run)
- Makes eslint a mandatory presubmit step (before if it wasn't installed,
it would skip the step with a soft warning).

BUG=642046
==========

to

==========
DevTools: Make eslint mandatory and check node.js/npm modules in presubmit

- Adds presubmit step to ensure users are running on node.js v4 or later
and installs node_modules using 'npm install'. If 'npm install' fails
(e.g. npm registry has an outage), it's a soft warning that doesn't fail
the presubmit check. Most likely, the user already has node_modules installed.

- Automatically installs local node.js for Linux users; Windows and Mac users 
have official node.js installers

- Even though this runs 'npm install' with every presubmit, if it has been 
installed once, running 'npm install' is a quick check (<1 sec to run)

- Makes eslint a mandatory presubmit step (before if it wasn't installed,
it would skip the step with a soft warning).

BUG=642046
==========

[chenwilliam, 2016-09-23 22:07:36]

PTAL. Changes since previous patchset:
- Automatically installs local node.js for Linux users; Windows and Mac users 
have official node.js installers

[lushnikov, 2016-09-27 03:55:13]

Summing up, we're supporting two workflows:
1. Chromium workflow. We assume there's no node.js/npm installed, rely on python
scripts and PRESUBMIT.py to do as much automation as possible.
2. Github workflow. Assume node/npm is installed

Since you have npm/node fetched automatically in (1), can we pull eslint
automatically as well?

Since there's node/npm in both cases, can we use package.json now?

https://codereview.chromium.org/2338753003/diff/100001/third_party/WebKit/Sou...
File third_party/WebKit/Source/devtools/scripts/lint_javascript.py (right):

https://codereview.chromium.org/2338753003/diff/100001/third_party/WebKit/Sou...
third_party/WebKit/Source/devtools/scripts/lint_javascript.py:60: print("Failed
to run eslint, run ./scripts/install_node_deps.py to install eslint")
wait, this doesn't install eslint any more? Should it?

[chenwilliam, 2016-09-27 17:30:58]

So there's two workflows but I would rephrase the assumption for chromium
workflow that we 1) see if we can use the global node.js/npm if it's installed
and a recent version, and then 2) fallback with installing them locally.

- Yep, eslint is pulled in automatically.
- Yep, we can use package.json now.

https://codereview.chromium.org/2338753003/diff/100001/third_party/WebKit/Sou...
File third_party/WebKit/Source/devtools/scripts/lint_javascript.py (right):

https://codereview.chromium.org/2338753003/diff/100001/third_party/WebKit/Sou...
third_party/WebKit/Source/devtools/scripts/lint_javascript.py:60: print("Failed
to run eslint, run ./scripts/install_node_deps.py to install eslint")
On 2016/09/27 03:55:13, lushnikov wrote:
> wait, this doesn't install eslint any more? Should it?

Running install_node_deps.py executes "npm install" which installs eslint (I
added it as a devdep in package.json). I removed the instructions to install
eslint globally to avoid versioning issues (e.g. people use eslint v2 for
another project).

[lushnikov, 2016-09-27 19:01:21]

Let's introduce a resolveNodePaths() function which returns a tuple of
(nodePath, npmPath) which satisfies out criterias.

The function should go ahead and install node/npm locally if it needs to and
return paths to the local instances

https://codereview.chromium.org/2338753003/diff/100001/third_party/WebKit/Sou...
File third_party/WebKit/Source/devtools/scripts/install_node_deps.py (right):

https://codereview.chromium.org/2338753003/diff/100001/third_party/WebKit/Sou...
third_party/WebKit/Source/devtools/scripts/install_node_deps.py:51: print('First
time run installs this in devtools/scripts/local_node/runtimes')
can we output this only as we actually fetch node/npm from the gs?

[chenwilliam, 2016-10-05 01:17:55]

Patchset #5 (id:120001) has been deleted

[chenwilliam, 2016-10-05 01:21:33]

PTAL. I've simplified the logic for resolving node/npm path and reduced the
print outputs.

https://codereview.chromium.org/2338753003/diff/100001/third_party/WebKit/Sou...
File third_party/WebKit/Source/devtools/scripts/install_node_deps.py (right):

https://codereview.chromium.org/2338753003/diff/100001/third_party/WebKit/Sou...
third_party/WebKit/Source/devtools/scripts/install_node_deps.py:51: print('First
time run installs this in devtools/scripts/local_node/runtimes')
On 2016/09/27 19:01:20, lushnikov wrote:
> can we output this only as we actually fetch node/npm from the gs?

Done.

[lushnikov, 2016-10-05 16:22:49]

https://codereview.chromium.org/2338753003/diff/140001/third_party/WebKit/Sou...
File third_party/WebKit/Source/devtools/PRESUBMIT.py (right):

https://codereview.chromium.org/2338753003/diff/140001/third_party/WebKit/Sou...
third_party/WebKit/Source/devtools/PRESUBMIT.py:40: def
_CheckNodeAndNPMModules(input_api, output_api):
do we really need this presubmit check?

looks like all the necessary job of installing nodes/npm will be done by the
lint_javascript.py - if needed

https://codereview.chromium.org/2338753003/diff/140001/third_party/WebKit/Sou...
File third_party/WebKit/Source/devtools/scripts/install_node_deps.py (right):

https://codereview.chromium.org/2338753003/diff/140001/third_party/WebKit/Sou...
third_party/WebKit/Source/devtools/scripts/install_node_deps.py:36: if
has_installed_local_node:
can we check for the local node binaries and return paths to them?

I'm afraid in case of error during local node installation, the directory might
exist, but there would be no binaries inside.

https://codereview.chromium.org/2338753003/diff/140001/third_party/WebKit/Sou...
third_party/WebKit/Source/devtools/scripts/install_node_deps.py:41:
print('Please install the latest node.js LTS version using the Mac or Windows
installer:')
let's prefix this with "ERROR:" so that it would be easier to spot in the
PRESUBMIT output

https://codereview.chromium.org/2338753003/diff/140001/third_party/WebKit/Sou...
File third_party/WebKit/Source/devtools/scripts/lint_javascript.py (right):

https://codereview.chromium.org/2338753003/diff/140001/third_party/WebKit/Sou...
third_party/WebKit/Source/devtools/scripts/lint_javascript.py:52: eslint_path =
path.join(devtools_path, "node_modules", ".bin", "eslint")
who's responsible for installing eslint?

[chenwilliam, 2016-10-05 17:59:19]

PTAL.

https://codereview.chromium.org/2338753003/diff/140001/third_party/WebKit/Sou...
File third_party/WebKit/Source/devtools/PRESUBMIT.py (right):

https://codereview.chromium.org/2338753003/diff/140001/third_party/WebKit/Sou...
third_party/WebKit/Source/devtools/PRESUBMIT.py:40: def
_CheckNodeAndNPMModules(input_api, output_api):
On 2016/10/05 16:22:49, lushnikov wrote:
> do we really need this presubmit check?
> 
> looks like all the necessary job of installing nodes/npm will be done by the
> lint_javascript.py - if needed

This is necessary to run "npm install", which is how eslint gets installed. We
could do the npm install step in the lint script, but as we add more build steps
using npm modules, it's better to do this as an explicit first step in the
presubmit script.

https://codereview.chromium.org/2338753003/diff/140001/third_party/WebKit/Sou...
File third_party/WebKit/Source/devtools/scripts/install_node_deps.py (right):

https://codereview.chromium.org/2338753003/diff/140001/third_party/WebKit/Sou...
third_party/WebKit/Source/devtools/scripts/install_node_deps.py:36: if
has_installed_local_node:
On 2016/10/05 16:22:49, lushnikov wrote:
> can we check for the local node binaries and return paths to them?
> 
> I'm afraid in case of error during local node installation, the directory
might
> exist, but there would be no binaries inside.

Done.

https://codereview.chromium.org/2338753003/diff/140001/third_party/WebKit/Sou...
third_party/WebKit/Source/devtools/scripts/install_node_deps.py:41:
print('Please install the latest node.js LTS version using the Mac or Windows
installer:')
On 2016/10/05 16:22:49, lushnikov wrote:
> let's prefix this with "ERROR:" so that it would be easier to spot in the
> PRESUBMIT output

Done.

https://codereview.chromium.org/2338753003/diff/140001/third_party/WebKit/Sou...
File third_party/WebKit/Source/devtools/scripts/lint_javascript.py (right):

https://codereview.chromium.org/2338753003/diff/140001/third_party/WebKit/Sou...
third_party/WebKit/Source/devtools/scripts/lint_javascript.py:52: eslint_path =
path.join(devtools_path, "node_modules", ".bin", "eslint")
On 2016/10/05 16:22:49, lushnikov wrote:
> who's responsible for installing eslint?

'npm install' is run as part of the PRESUBMIT script, please see the comment in
that file.

https://codereview.chromium.org/2338753003/diff/180001/third_party/WebKit/Sou...
File third_party/WebKit/Source/devtools/scripts/install_node_deps.py (right):

https://codereview.chromium.org/2338753003/diff/180001/third_party/WebKit/Sou...
third_party/WebKit/Source/devtools/scripts/install_node_deps.py:41:
shutil.rmtree(local_node_runtimes_path)
if needed, cleans up a previous partial installation

[lushnikov, 2016-10-07 17:05:43]

overall, looks good! Let's clean a few nits and it's ready to go

https://codereview.chromium.org/2338753003/diff/140001/third_party/WebKit/Sou...
File third_party/WebKit/Source/devtools/PRESUBMIT.py (right):

https://codereview.chromium.org/2338753003/diff/140001/third_party/WebKit/Sou...
third_party/WebKit/Source/devtools/PRESUBMIT.py:40: def
_CheckNodeAndNPMModules(input_api, output_api):
On 2016/10/05 17:59:19, chenwilliam wrote:
> On 2016/10/05 16:22:49, lushnikov wrote:
> > do we really need this presubmit check?
> > 
> > looks like all the necessary job of installing nodes/npm will be done by the
> > lint_javascript.py - if needed
> 
> This is necessary to run "npm install", which is how eslint gets installed. We
> could do the npm install step in the lint script, but as we add more build
steps
> using npm modules, it's better to do this as an explicit first step in the
> presubmit script.

Shell we pursue the hermetic build for the github workflow?

https://codereview.chromium.org/2338753003/diff/180001/third_party/WebKit/Sou...
File third_party/WebKit/Source/devtools/scripts/install_node_deps.py (right):

https://codereview.chromium.org/2338753003/diff/180001/third_party/WebKit/Sou...
third_party/WebKit/Source/devtools/scripts/install_node_deps.py:20:
LOCAL_NODE_VERSION = node.DEFAULT_VERSION
let's treat node.py as a third-party code and rely solely on it's API.

so instead of getting LOCAL_NODE_VERSION from node.DEFAULT_VERSION, let's define
it here, and pass it over to node.py in install_node() function

https://codereview.chromium.org/2338753003/diff/180001/third_party/WebKit/Sou...
third_party/WebKit/Source/devtools/scripts/install_node_deps.py:63:
print('Installing node.js locally at devtools/scripts/local_node/runtimes')
locally at local_node_runtimes_path

[chenwilliam, 2016-10-10 19:36:18]

PTAL.

https://codereview.chromium.org/2338753003/diff/140001/third_party/WebKit/Sou...
File third_party/WebKit/Source/devtools/PRESUBMIT.py (right):

https://codereview.chromium.org/2338753003/diff/140001/third_party/WebKit/Sou...
third_party/WebKit/Source/devtools/PRESUBMIT.py:40: def
_CheckNodeAndNPMModules(input_api, output_api):
On 2016/10/07 17:05:43, lushnikov wrote:
> On 2016/10/05 17:59:19, chenwilliam wrote:
> > On 2016/10/05 16:22:49, lushnikov wrote:
> > > do we really need this presubmit check?
> > > 
> > > looks like all the necessary job of installing nodes/npm will be done by
the
> > > lint_javascript.py - if needed
> > 
> > This is necessary to run "npm install", which is how eslint gets installed.
We
> > could do the npm install step in the lint script, but as we add more build
> steps
> > using npm modules, it's better to do this as an explicit first step in the
> > presubmit script.
> 
> Shell we pursue the hermetic build for the github workflow?

I'm currently going through the compliance review for the npm modules repo
(which would be used for buildbots) so for now we can't do a hermetic build
using a git checkout of the npm modules. If we're concerned about versioning, we
can shrinkwrap our package.json which locks down the versions of the entire
dependency tree.  For now, I think because it's just eslint we should be OK.

https://codereview.chromium.org/2338753003/diff/180001/third_party/WebKit/Sou...
File third_party/WebKit/Source/devtools/scripts/install_node_deps.py (right):

https://codereview.chromium.org/2338753003/diff/180001/third_party/WebKit/Sou...
third_party/WebKit/Source/devtools/scripts/install_node_deps.py:20:
LOCAL_NODE_VERSION = node.DEFAULT_VERSION
On 2016/10/07 17:05:43, lushnikov wrote:
> let's treat node.py as a third-party code and rely solely on it's API.
> 
> so instead of getting LOCAL_NODE_VERSION from node.DEFAULT_VERSION, let's
define
> it here, and pass it over to node.py in install_node() function

Done.

https://codereview.chromium.org/2338753003/diff/180001/third_party/WebKit/Sou...
third_party/WebKit/Source/devtools/scripts/install_node_deps.py:63:
print('Installing node.js locally at devtools/scripts/local_node/runtimes')
On 2016/10/07 17:05:43, lushnikov wrote:
> locally at local_node_runtimes_path

Done.

[lushnikov, 2016-10-12 22:10:19]

i tried it, it worked seamlessly for me on Linux

lgtm % comments

https://codereview.chromium.org/2338753003/diff/200001/third_party/WebKit/Sou...
File third_party/WebKit/Source/devtools/scripts/local_node/node.py (right):

https://codereview.chromium.org/2338753003/diff/200001/third_party/WebKit/Sou...
third_party/WebKit/Source/devtools/scripts/local_node/node.py:17: print('Usage:
{} <version>'.format(sys.argv[0]))
you already have a way to pass Node version in via the ENV - no need to add
another one.

[chenwilliam, 2016-10-17 19:32:27]

https://codereview.chromium.org/2338753003/diff/200001/third_party/WebKit/Sou...
File third_party/WebKit/Source/devtools/scripts/local_node/node.py (right):

https://codereview.chromium.org/2338753003/diff/200001/third_party/WebKit/Sou...
third_party/WebKit/Source/devtools/scripts/local_node/node.py:17: print('Usage:
{} <version>'.format(sys.argv[0]))
On 2016/10/12 22:10:19, lushnikov wrote:
> you already have a way to pass Node version in via the ENV - no need to add
> another one.

Done.

[chenwilliam, 2016-10-17 19:32:36]

The CQ bit was checked by chenwilliam@chromium.org

[chenwilliam, 2016-10-17 19:32:36]

The patchset sent to the CQ was uploaded after l-g-t-m from
lushnikov@chromium.org
Link to the patchset: https://codereview.chromium.org/2338753003/#ps220001
(title: "Fix node.py")

[commit-bot: I haz the power, 2016-10-17 19:33:00]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-10-17 21:06:02]

Description was changed from

==========
DevTools: Make eslint mandatory and check node.js/npm modules in presubmit

- Adds presubmit step to ensure users are running on node.js v4 or later
and installs node_modules using 'npm install'. If 'npm install' fails
(e.g. npm registry has an outage), it's a soft warning that doesn't fail
the presubmit check. Most likely, the user already has node_modules installed.

- Automatically installs local node.js for Linux users; Windows and Mac users 
have official node.js installers

- Even though this runs 'npm install' with every presubmit, if it has been 
installed once, running 'npm install' is a quick check (<1 sec to run)

- Makes eslint a mandatory presubmit step (before if it wasn't installed,
it would skip the step with a soft warning).

BUG=642046
==========

to

==========
DevTools: Make eslint mandatory and check node.js/npm modules in presubmit

- Adds presubmit step to ensure users are running on node.js v4 or later
and installs node_modules using 'npm install'. If 'npm install' fails
(e.g. npm registry has an outage), it's a soft warning that doesn't fail
the presubmit check. Most likely, the user already has node_modules installed.

- Automatically installs local node.js for Linux users; Windows and Mac users 
have official node.js installers

- Even though this runs 'npm install' with every presubmit, if it has been 
installed once, running 'npm install' is a quick check (<1 sec to run)

- Makes eslint a mandatory presubmit step (before if it wasn't installed,
it would skip the step with a soft warning).

BUG=642046
==========

[commit-bot: I haz the power, 2016-10-17 21:06:03]

Committed patchset #9 (id:220001)

[commit-bot: I haz the power, 2016-10-17 21:09:10]

Description was changed from

==========
DevTools: Make eslint mandatory and check node.js/npm modules in presubmit

- Adds presubmit step to ensure users are running on node.js v4 or later
and installs node_modules using 'npm install'. If 'npm install' fails
(e.g. npm registry has an outage), it's a soft warning that doesn't fail
the presubmit check. Most likely, the user already has node_modules installed.

- Automatically installs local node.js for Linux users; Windows and Mac users 
have official node.js installers

- Even though this runs 'npm install' with every presubmit, if it has been 
installed once, running 'npm install' is a quick check (<1 sec to run)

- Makes eslint a mandatory presubmit step (before if it wasn't installed,
it would skip the step with a soft warning).

BUG=642046
==========

to

==========
DevTools: Make eslint mandatory and check node.js/npm modules in presubmit

- Adds presubmit step to ensure users are running on node.js v4 or later
and installs node_modules using 'npm install'. If 'npm install' fails
(e.g. npm registry has an outage), it's a soft warning that doesn't fail
the presubmit check. Most likely, the user already has node_modules installed.

- Automatically installs local node.js for Linux users; Windows and Mac users
have official node.js installers

- Even though this runs 'npm install' with every presubmit, if it has been
installed once, running 'npm install' is a quick check (<1 sec to run)

- Makes eslint a mandatory presubmit step (before if it wasn't installed,
it would skip the step with a soft warning).

BUG=642046

Committed: https://crrev.com/6d7f23b089bcfd951446564995916395b579140d
Cr-Commit-Position: refs/heads/master@{#425777}
==========

[commit-bot: I haz the power, 2016-10-17 21:09:13]

Patchset 9 (id:??) landed as
https://crrev.com/6d7f23b089bcfd951446564995916395b579140d
Cr-Commit-Position: refs/heads/master@{#425777}