Dart: Changes to support building for Android.

Dart: Changes to support building for Android.

This change builds and runs gen_snapshot using only the host
toolchain, and so enables the Android build of Dart. It
updates the Dart revision to pull in these changes:

https://codereview.chromium.org/863173003/

BUG=
R=abarth@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/42969150f450c048c79dc0785e0d74b1c883a47c

[zra, 2015-01-26 21:21:47]

zra@google.com changed reviewers:
+ abarth@chromium.org

[zra, 2015-01-26 21:21:48]

I couldn't quickly figure out how hack the test scripts to upload Dart code to
the device needed for dart_unittests. So this change does not enable any
testing. @abarth, do you know who knows how to do that?

[abarth-chromium, 2015-01-26 21:24:54]

On 2015/01/26 at 21:21:48, zra wrote:
> I couldn't quickly figure out how hack the test scripts to upload Dart code to
the device needed for dart_unittests. So this change does not enable any
testing. @abarth, do you know who knows how to do that?

Generally speaking, we don't know now to run unittests on devices yet.  :)

[abarth-chromium, 2015-01-26 21:25:17]

lgtm

[zra, 2015-01-26 22:47:56]

Committed patchset #1 (id:1) manually as
42969150f450c048c79dc0785e0d74b1c883a47c (presubmit successful).

[qsr, 2015-01-28 14:51:15]

On 2015/01/26 21:24:54, abarth wrote:
> On 2015/01/26 at 21:21:48, zra wrote:
> > I couldn't quickly figure out how hack the test scripts to upload Dart code
to
> the device needed for dart_unittests. So this change does not enable any
> testing. @abarth, do you know who knows how to do that?
> 
> Generally speaking, we don't know now to run unittests on devices yet.  :)

 We do run unit tests on devices since last week. We will be running app test
when https://codereview.chromium.org/881753002/ lands. Now test have to be self
contained. We cannot run anything that depend on the source filesystem.