Improve Observatory debugger behaviour when an isolate exits with unhandled exceptions

Improve Observatory debugger behaviour when an isolate exits with unhandled exceptions

- When an isolate is paused at exit and has a sticky error, have the debugger display the error.
- Add --pause-isolates-on-unhandled-exceptions flag which sets a default value for break-on-exception.
- Have the debugger display help text about 'set break-on-exception' and '--pause-isolates-on-unhandled-exceptions'
- Signal an unhandled exception even if no client is connected to Observatory.

R=rmacnak@google.com

Committed: https://github.com/dart-lang/sdk/commit/ec020a301b7885a00862531f031efd83eee83f14

[Cutch, 2016-01-26 17:51:17]

Description was changed from

==========
Improve Observatory debugger behaviour when an isolate exits with unhandled
exceptions

BUG=
==========

to

==========
Improve Observatory debugger behaviour when an isolate exits with unhandled
exceptions

- Have the debugger display the error, when an isolate is paused at exit and has
a sticky error.
- Add --pause-isolates-on-unhandled-exceptions flag which sets a default value
for break-on-exception.
- Have the debugger display help text about 'set break-on-exception' and
'--pause-isolates-on-unhandled-exceptions'
- Signal an unhandled exception even if no client is connected to Observatory.
==========

[Cutch, 2016-01-26 17:51:17]

johnmccutchan@google.com changed reviewers:
+ bak@google.com, rmacnak@google.com

[Cutch, 2016-01-26 17:51:53]

Description was changed from

==========
Improve Observatory debugger behaviour when an isolate exits with unhandled
exceptions

- Have the debugger display the error, when an isolate is paused at exit and has
a sticky error.
- Add --pause-isolates-on-unhandled-exceptions flag which sets a default value
for break-on-exception.
- Have the debugger display help text about 'set break-on-exception' and
'--pause-isolates-on-unhandled-exceptions'
- Signal an unhandled exception even if no client is connected to Observatory.
==========

to

==========
Improve Observatory debugger behaviour when an isolate exits with unhandled
exceptions

- When an isolate is paused at exit and has a sticky error, have the debugger
display the error.
- Add --pause-isolates-on-unhandled-exceptions flag which sets a default value
for break-on-exception.
- Have the debugger display help text about 'set break-on-exception' and
'--pause-isolates-on-unhandled-exceptions'
- Signal an unhandled exception even if no client is connected to Observatory.
==========

[rmacnak, 2016-01-26 17:56:24]

lgtm

[Cutch, 2016-01-26 18:12:50]

Description was changed from

==========
Improve Observatory debugger behaviour when an isolate exits with unhandled
exceptions

- When an isolate is paused at exit and has a sticky error, have the debugger
display the error.
- Add --pause-isolates-on-unhandled-exceptions flag which sets a default value
for break-on-exception.
- Have the debugger display help text about 'set break-on-exception' and
'--pause-isolates-on-unhandled-exceptions'
- Signal an unhandled exception even if no client is connected to Observatory.
==========

to

==========
Improve Observatory debugger behaviour when an isolate exits with unhandled
exceptions

- When an isolate is paused at exit and has a sticky error, have the debugger
display the error.
- Add --pause-isolates-on-unhandled-exceptions flag which sets a default value
for break-on-exception.
- Have the debugger display help text about 'set break-on-exception' and
'--pause-isolates-on-unhandled-exceptions'
- Signal an unhandled exception even if no client is connected to Observatory.

R=rmacnak@google.com

Committed:
https://github.com/dart-lang/sdk/commit/ec020a301b7885a00862531f031efd83eee83f14
==========

[Cutch, 2016-01-26 18:12:51]

Committed patchset #2 (id:20001) manually as
ec020a301b7885a00862531f031efd83eee83f14 (presubmit successful).