Update observatory_tool.py to remove package-root

Update observatory_tool.py to remove package-root

BUG=
R=johnmccutchan@google.com

Committed: https://github.com/dart-lang/sdk/commit/9f3b5d8680f1b264d6c9300b3759383cdd6561d8

[Bill Hesse, 2016-09-16 14:36:51]

whesse@google.com changed reviewers:
+ johnmccutchan@google.com

[Bill Hesse, 2016-09-16 14:36:52]

I think this is the best way to solve this - I don't see any use for the option
any more.  I think it is breaking the debian package builder.

[Cutch, 2016-09-16 14:41:27]

LGTM but does this mean that we are using the same .packages as the sdk
repository? Observatory depends on the charted package.

[Bill Hesse, 2016-09-19 08:09:28]

On 2016/09/16 14:41:27, Cutch wrote:
> LGTM but does this mean that we are using the same .packages as the sdk
> repository? Observatory depends on the charted package.

The package root here was only used to run pub, using the dart executable and
the pub source code, when the SDK wasn't compiled yet.  Not as source for
observatory at all.

[Bill Hesse, 2016-09-19 08:11:36]

Description was changed from

==========
Update observatory_tool.py to remove package-root

BUG=
==========

to

==========
Update observatory_tool.py to remove package-root

BUG=
R=johnmccutchan@google.com

Committed:
https://github.com/dart-lang/sdk/commit/9f3b5d8680f1b264d6c9300b3759383cdd6561d8
==========

[Bill Hesse, 2016-09-19 08:11:38]

Committed patchset #1 (id:1) manually as
9f3b5d8680f1b264d6c9300b3759383cdd6561d8 (presubmit successful).