Do not collect stack trace unnecessarily
Do not collect stack trace unnecessarily

The debugger collected stack traces on each exception throw
even when the debugger client specifies "no pause on exception".
This fixes the asserts that Anton saw in some tests.
Review URL: https://chromiumcodereview.appspot.com//10645003

git-svn-id: c93d8a2297af3b929165606efe145742a534bc71@8996 260f80e4-7a28-3924-810f-c04153c831b5

dart-lang/sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk