Two issues:
1. Some exceptions don't derive from Exception (for example
NoSuchMethodError). So to avoid problems in checked builds,
CaughtException.exception needs to have type Object.
2. When an exception is caught by the unittest framework, it prints it
using its toString() method. So in order to see the stack trace of
the CaughtException nested in an AnalysisException, we need
AnalysisException's toString() to print both the exception and its
cause (if any).
R=brianwilkerson@google.com, jwren@google.com, scheglov@google.com
Review URL: https://codereview.chromium.org//304293010
git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@37186 260f80e4-7a28-3924-810f-c04153c831b5
paulberry@google.com
238ea2c84e