Fix canonicalization of types.

Fix canonicalization of types.
Add functions retrieving canonical types by their index or vice versa (used by
a future cl supporting types in vm service).
Add getters for type argument instantiations (used by future cl).

R=hausner@google.com

Committed: https://code.google.com/p/dart/source/detail?r=34128

[hausner, 2014-03-19 18:27:28]

LGTM

https://codereview.chromium.org/203443012/diff/1/runtime/vm/object.cc
File runtime/vm/object.cc (right):

https://codereview.chromium.org/203443012/diff/1/runtime/vm/object.cc#newcode...
runtime/vm/object.cc:3259: if (types.IsNull() || !types.IsArray()) {
At this point, types should always be an array, right? the case where it is a
type is handled in the first if statement. Same comment in the two functions
below.

[regis, 2014-03-19 18:46:00]

Thanks!

https://codereview.chromium.org/203443012/diff/1/runtime/vm/object.cc
File runtime/vm/object.cc (right):

https://codereview.chromium.org/203443012/diff/1/runtime/vm/object.cc#newcode...
runtime/vm/object.cc:3259: if (types.IsNull() || !types.IsArray()) {
On 2014/03/19 18:27:28, hausner wrote:
> At this point, types should always be an array, right? the case where it is a
> type is handled in the first if statement. Same comment in the two functions
> below.

Correct. I removed || !types.IsArray() here and below.

[regis, 2014-03-19 18:49:02]

Committed patchset #2 manually as r34128 (presubmit successful).