Print "Building $app..." before any transformers start running.

Print "Building $app..." before any transformers start running.

R=rnystrom@google.com
BUG=17603
Committed: https://code.google.com/p/dart/source/detail?r=34149

[Bob Nystrom, 2014-03-19 20:51:33]

I'm not sure I understand this. Transformers can start running as soon as the
environment is created since that:

1. Loads the transformers, which may require transformers to run.
2. Adds all of sources in "lib" and "asset" for every package in the package
graph.

Do we need a different approach here?

[nweiz, 2014-03-19 20:54:24]

On 2014/03/19 20:51:33, Bob Nystrom wrote:
> I'm not sure I understand this. Transformers can start running as soon as the
> environment is created since that:
> 
> 1. Loads the transformers, which may require transformers to run.
> 2. Adds all of sources in "lib" and "asset" for every package in the package
> graph.
> 
> Do we need a different approach here?

Sorry, I should have been clearer. This just ensures that the message is printed
before transformers are run on stuff in web/ and other entrypoint files. This
was almost always happening anyway, this just avoids a race condition that was
making a test flaky.

[Bob Nystrom, 2014-03-19 21:55:00]

lgtm

[nweiz, 2014-03-20 00:19:10]

Committed patchset #1 manually as r34149 (presubmit successful).