some error dialog styling issues

@gaurave, @ussuri, fixes https://github.com/dart-lang/chromedeveditor/issues/2708

- the error dialog now has a max size, and the message will scroll within that if necessary
- fixed some issues with joining the message and exception

before:
![screen shot 2014-07-01 at 4 42 54 pm](https://cloud.githubusercontent.com/assets/1269969/3450536/00422524-017e-11e4-9563-bedb92f94b9f.png)

after:
![screen shot 2014-07-01 at 5 01 23 pm](https://cloud.githubusercontent.com/assets/1269969/3450540/07f38d9e-017e-11e4-8a9f-b3e8b1159fa5.png)

Good to know, thanks.
On Jul 2, 2014 11:37 AM, "Hoà V. DINH" <notifications@github.com> wrote:

> In ide/app/spark.dart:
>
> > @@ -618,21 +619,25 @@ abstract class Spark
> >        _errorDialog.getShadowDomElement("#closingX").onClick.listen(_hideBackdropOnClick);
> >      }
> >
> > -    if (exception is SparkException) {
> > -        message = exception.message;
> > -    } else if (exception != null) {
> > -      if (message == null) message = '';
> > -      // TODO(grv): wrap all exceptions as spark exception,
> > -      // and show 'Unexpected error.' to the user for unknown exceptions.
> > -      message = message + ' : ' + exception.toString();
> > -      // Log the actual exception on console if running in developer mode.
> > -      if (SparkFlags.developerMode) {
> > -        window.console.log(exception);
> > +    if (exception != null && SparkFlags.developerMode) {
> > +      window.console.log(exception);
>
> The content of the object can be browsed / collapsed / expanded (like
> console.log() in JS) vs just having a static line to text. It's useful to
> print hash map or arrays.
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/dart-lang/chromedeveditor/pull/2787/files#r14485437>.
>