Add Dart_GetSupertype to the dart debugger API so that the dartium

Add Dart_GetSupertype to the dart debugger API so that the dartium
debugger interface can use this instead of Dart_GetSuperClass.

R=regis@google.com

Committed: https://code.google.com/p/dart/source/detail?r=24648

[regis, 2013-07-01 16:29:27]

https://codereview.chromium.org/18238003/diff/15001/runtime/vm/debugger_api_i...
File runtime/vm/debugger_api_impl.cc (right):

https://codereview.chromium.org/18238003/diff/15001/runtime/vm/debugger_api_i...
runtime/vm/debugger_api_impl.cc:533: for (intptr_t i = 0; i <
num_expected_type_arguments; i++) {
It is not correct to start at index 0. Since you call FinalizeType below, you
only want the type parameters of super_cls, but not those of its own super type.
You should start at index super_cls.NumTypeArguments() -
super_cls.NumTypeParameters(). It will be 0 if super_cls has no super class, but
larger than 0 if super_cls has a type parameterized super class.

Another, maybe simpler, approach would be to truncate the type argument vector
of cls to length super_cls.NumTypeArguments() and canonicalize the new type
(without finalization).

[siva, 2013-07-01 18:45:15]

Addressed review comment.

PTAL

https://codereview.chromium.org/18238003/diff/15001/runtime/vm/debugger_api_i...
File runtime/vm/debugger_api_impl.cc (right):

https://codereview.chromium.org/18238003/diff/15001/runtime/vm/debugger_api_i...
runtime/vm/debugger_api_impl.cc:533: for (intptr_t i = 0; i <
num_expected_type_arguments; i++) {
As discussed offline I went with the adjustment to start index method as the
more simpler approach to truncate the type argument vector causes issues with
the type not being finalized.

Added a test for this condition to the test case.

On 2013/07/01 16:29:27, regis wrote:
> It is not correct to start at index 0. Since you call FinalizeType below, you
> only want the type parameters of super_cls, but not those of its own super
type.
> You should start at index super_cls.NumTypeArguments() -
> super_cls.NumTypeParameters(). It will be 0 if super_cls has no super class,
but
> larger than 0 if super_cls has a type parameterized super class.
> 
> Another, maybe simpler, approach would be to truncate the type argument vector
> of cls to length super_cls.NumTypeArguments() and canonicalize the new type
> (without finalization).

[regis, 2013-07-01 18:55:49]

LGTM

https://codereview.chromium.org/18238003/diff/22001/runtime/vm/debugger_api_i...
File runtime/vm/debugger_api_impl.cc (right):

https://codereview.chromium.org/18238003/diff/22001/runtime/vm/debugger_api_i...
runtime/vm/debugger_api_impl.cc:536: ASSERT(type_args_array.Length() > (i +
index_offset));
Isn't this ASSERT already checked as part of TypeAt below?

[siva, 2013-07-01 19:41:40]

https://codereview.chromium.org/18238003/diff/22001/runtime/vm/debugger_api_i...
File runtime/vm/debugger_api_impl.cc (right):

https://codereview.chromium.org/18238003/diff/22001/runtime/vm/debugger_api_i...
runtime/vm/debugger_api_impl.cc:536: ASSERT(type_args_array.Length() > (i +
index_offset));
True it is, removed the assert.

On 2013/07/01 18:55:49, regis wrote:
> Isn't this ASSERT already checked as part of TypeAt below?

[siva, 2013-07-01 19:46:45]

Committed patchset #5 manually as r24648 (presubmit successful).