Fix Dart_RemoveBreakpoint
Fix Dart_RemoveBreakpoint

The debugger code assumed that breakpoints can only be removed
while the debugger is paused. That is not true. An embedder can
remove breakpoints while the isolate is idle and running any
Dart code.

Fix for issue 3781 (http://dartbug.com/3781)
Review URL: https://chromiumcodereview.appspot.com//10698051

git-svn-id: c93d8a2297af3b929165606efe145742a534bc71@9258 260f80e4-7a28-3924-810f-c04153c831b5

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