Fixing up test_app.dart

This should address having issues with the `app.window` related tests on MacOSX Dartium. I was not able to succfully run on Canary, not sure if its my machine. Getting the following message

```
–(~/dart/chrome.dart)–($ dart tool/hop_runner.dart run_test_harness 
[40518:23811:0903/194047:WARNING:external_pref_loader.cc(127)] You are using an old-style extension deployment method (external_extensions.json), which will soon be deprecated. (see http://code.google.com/chrome/extensions/external_extensions.html )
```
Could some review and try out before merging? @kevmoo @devoncarew @DrMarcII @rmsmith looking to make a 0.3.0 release by tomorrow. 

Status of the unit tests: `Total 45 passed, 0 failed, 3 errors` 

The `chrome.storage` error is due to me not being signed into Dartium with my google account. Maybe that should be mocked out? 

Error with `chrome.app.window` is the `top` value is not the same as what was passed in to `app.window.create()`. Not sure if the top value is guaranteed to be set. So it might not really be an error. 

The third error is something with TcpClient callbacks, might be a simple fix. Have not fully looked into it. 

 
![screen shot 2013-09-03 at 7 33 21 pm](https://f.cloud.github.com/assets/654526/1077744/91938194-150c-11e3-8072-344545215f26.png)

![screen shot 2013-09-03 at 7 29 18 pm](https://f.cloud.github.com/assets/654526/1077746/9756193e-150c-11e3-867e-1cfea915b71a.png)