Only propagate reload errors when there are Dart frames on the stack.

Only propagate reload errors when there are Dart frames on the stack.

- [x] Check for Dart frames on the stack before propagating an exception.
- [x] Never propagate an uncaught exception that occurs during reload to the program.
- [x] Add a unit test to verify that bad imports during a reload do not crash the VM

Fixes #29085

BUG=
R=rmacnak@google.com

Committed: https://github.com/dart-lang/sdk/commit/4d7acb34d94b82e7fdcbf05b832e844eef5847c4

[Cutch, 2017-03-15 23:51:14]

Description was changed from

==========
Only propagate reload errors when there are Dart frames on the stack.

- [x] Check for Dart frames on the stack before propagating an exception.
- [x] Never propagate an uncaught exception that occurs during reload to the
program.
- [x] Add a unit test to verify that bad imports during a reload do not crash
the VM

Fixes #29085

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

to

==========
Only propagate reload errors when there are Dart frames on the stack.

- [x] Check for Dart frames on the stack before propagating an exception.
- [x] Never propagate an uncaught exception that occurs during reload to the
program.
- [x] Add a unit test to verify that bad imports during a reload do not crash
the VM

Fixes #29085

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

[Cutch, 2017-03-15 23:51:14]

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

[rmacnak, 2017-03-16 17:49:30]

LGTM

[Cutch, 2017-03-16 17:51:08]

Description was changed from

==========
Only propagate reload errors when there are Dart frames on the stack.

- [x] Check for Dart frames on the stack before propagating an exception.
- [x] Never propagate an uncaught exception that occurs during reload to the
program.
- [x] Add a unit test to verify that bad imports during a reload do not crash
the VM

Fixes #29085

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

to

==========
Only propagate reload errors when there are Dart frames on the stack.

- [x] Check for Dart frames on the stack before propagating an exception.
- [x] Never propagate an uncaught exception that occurs during reload to the
program.
- [x] Add a unit test to verify that bad imports during a reload do not crash
the VM

Fixes #29085

BUG=
R=rmacnak@google.com

Committed:
https://github.com/dart-lang/sdk/commit/4d7acb34d94b82e7fdcbf05b832e844eef5847c4
==========

[Cutch, 2017-03-16 17:51:09]

Committed patchset #2 (id:20001) manually as
4d7acb34d94b82e7fdcbf05b832e844eef5847c4 (presubmit successful).

[siva, 2017-03-16 18:09:45]

asiva@google.com changed reviewers:
+ asiva@google.com

[siva, 2017-03-16 18:09:45]

DBC

https://codereview.chromium.org/2748353004/diff/20001/runtime/vm/isolate_relo...
File runtime/vm/isolate_reload.cc (right):

https://codereview.chromium.org/2748353004/diff/20001/runtime/vm/isolate_relo...
runtime/vm/isolate_reload.cc:637: BackgroundCompiler::Enable();
We should probably enable the background compiler as the last step after all the
checks are done.