Handle contexts which have been optimized out.

Handle contexts which have been optimized out.

Expand list of expected object types seen on the stack.

BUG=
R=asiva@google.com

Committed: https://code.google.com/p/dart/source/detail?r=32708

[turnidge, 2014-02-13 18:55:49]

https://codereview.chromium.org/163433003/diff/1/runtime/vm/debugger.cc
File runtime/vm/debugger.cc (right):

https://codereview.chromium.org/163433003/diff/1/runtime/vm/debugger.cc#newco...
runtime/vm/debugger.cc:613: return Context::null();
I decided to use Context::null() to represent an optimized-out context.  All
other cases which return Context::null() should now be tagged as UNREACHABLE.

https://codereview.chromium.org/163433003/diff/1/runtime/vm/deopt_instruction...
File runtime/vm/deopt_instructions.cc (right):

https://codereview.chromium.org/163433003/diff/1/runtime/vm/deopt_instruction...
runtime/vm/deopt_instructions.cc:372: obj.IsField());
...or I could just eliminate this ASSERT entirely...

[siva, 2014-02-13 22:58:40]

LGTM with one comment.

https://codereview.chromium.org/163433003/diff/1/runtime/vm/deopt_instruction...
File runtime/vm/deopt_instructions.cc (right):

https://codereview.chromium.org/163433003/diff/1/runtime/vm/deopt_instruction...
runtime/vm/deopt_instructions.cc:372: obj.IsField());
On 2014/02/13 18:55:49, turnidge wrote:
> ...or I could just eliminate this ASSERT entirely...

Under what circumstances can we expect to see a Class object and Field object in
a dart frame? Maybe you should add a comment here
explaining that.

[turnidge, 2014-02-14 16:36:27]

https://codereview.chromium.org/163433003/diff/1/runtime/vm/deopt_instruction...
File runtime/vm/deopt_instructions.cc (right):

https://codereview.chromium.org/163433003/diff/1/runtime/vm/deopt_instruction...
runtime/vm/deopt_instructions.cc:372: obj.IsField());
On 2014/02/13 22:58:40, siva wrote:
> On 2014/02/13 18:55:49, turnidge wrote:
> > ...or I could just eliminate this ASSERT entirely...
> 
> Under what circumstances can we expect to see a Class object and Field object
in
> a dart frame? Maybe you should add a comment here
> explaining that.

I don't know why this happened yet.  I was hoping you would know :-/.

[turnidge, 2014-02-14 18:02:58]

Added a TODO to figure out the reason for these.  My guess is that it has to do
with type feedback, but not sure.

[turnidge, 2014-02-14 18:04:53]

Committed patchset #2 manually as r32708 (presubmit successful).