Rework how isolates are generated in MB.

Rework how isolates are generated in MB.

This patch changes how MB will generate the .isolate files
for a GN build:

First, we rename 'ninja_to_gn.pyl' to 'gn_isolate_map.pyl',
and change it from a straight compile_target -> gn_label map to
a map of compile_target -> { "label": gn_label, "type": string,
"args": optional list<string> }.

Valid values for "type" are
"windowed_test_launcher"
: the test is a gtest-based test that uses the
  'brave-new-test-launcher' from //base/test:test_support and
  needs to run under Xvfb if run on an X11-based platform
  (i.e., if use_x11=true in GN).
"console_test_launcher"
: the test is a gtest-based test that uses the
  'brave-new-test-launcher' from //base/test:test_support but does
  not need Xvfb.
"raw"
: the test is just an executable and may take an optional list
  of command-line arguments (specified in the 'args' key),
  but does not need any extra files or other special processing.
"unknown"
: (the default), which indicates that we don't know what the command
  line needs to be (this is a fatal error).

Second, we read the new file in, and build a lookup map of test
types to command lines. We will probably need to keep iterating
on the list of test types and command lines, and perhaps provide
some escape hatches so that we can handle the full variety of tests.

[email protected]
BUG=503942, 504079
Committed: https://crrev.com/a55584f181b9ca9c6806f0d41eb4112e47a16e67
Cr-Commit-Position: refs/heads/master@{#339804}

[Dirk Pranke, 2015-07-21 21:37:02]

TBR'ing since this patch is excerpted from
https://codereview.chromium.org/1206033005/ where it was LGTM'ed.

(This patch only changes MB and does not add any of the new isolate logic).

[Dirk Pranke, 2015-07-21 23:40:39]

The CQ bit was checked by [email protected]

[commit-bot: I haz the power, 2015-07-21 23:41:30]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1239343003/1

[commit-bot: I haz the power, 2015-07-22 00:52:54]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-07-22 00:54:24]

Patchset 1 (id:??) landed as
https://crrev.com/a55584f181b9ca9c6806f0d41eb4112e47a16e67
Cr-Commit-Position: refs/heads/master@{#339804}

[M-A Ruel, 2015-07-22 18:22:42]

a few nits

https://codereview.chromium.org/1239343003/diff/1/testing/buildbot/manage.py
File testing/buildbot/manage.py (right):

https://codereview.chromium.org/1239343003/diff/1/testing/buildbot/manage.py#...
testing/buildbot/manage.py:272: ninja_targets = dict((k, v['label']) for k, v in
gn_isolate_map.items())
Stylistically, I would have preferred:
ninja_targets = {k: v['label'] for k, v in gn_isolate_map.iteritems()}

:)

https://codereview.chromium.org/1239343003/diff/1/tools/mb/mb.py
File tools/mb/mb.py (right):

https://codereview.chromium.org/1239343003/diff/1/tools/mb/mb.py#newcode480
tools/mb/mb.py:480: 'read_only': 1,
Not needed

[Dirk Pranke, 2015-07-22 18:46:02]

On 2015/07/22 18:22:42, M-A Ruel wrote:
> a few nits
>

I think you gave me this feedback before somewhere and I must've 
dropped it on the floor. Sorry!

I will fix in a follow-up patch.