Fix bug in Dart_GetTypeOfExternalTypedData.

Fix bug in Dart_GetTypeOfExternalTypedData.

This API function would return true for typed data view objects, even
if the view has a non-external data object underneath.

It is used e.g. by Builtin_LoadSource. This function copies the data
object for internal typed-data objects.
When it wrongly be identifies a view as external, it consequently results
in crash/undefined behavior because GC may interfere with this internal
data pointer.

BUG=
R=asiva@google.com, koda@google.com

Committed: https://github.com/dart-lang/sdk/commit/19bb19d7162cfae8e9fc1981fc12d8c75a2f83b0

[Florian Schneider, 2015-06-12 16:20:46]

fschneider@google.com changed reviewers:
+ asiva@google.com, koda@google.com

[koda, 2015-06-12 16:24:23]

Please also add an ASSERT that the address of the typed data contents we hand
out is *not* contained within the heap (Heap::Contains).

[koda, 2015-06-12 16:26:00]

On 2015/06/12 16:24:23, koda wrote:
> Please also add an ASSERT that the address of the typed data contents we hand
> out is *not* contained within the heap (Heap::Contains).

Or, if you prefer, I can do this in a follow-up CL.

The fix itself LGTM.

[siva, 2015-06-12 16:27:06]

lgtm

https://codereview.chromium.org/1182123002/diff/1/runtime/vm/dart_api_impl.cc
File runtime/vm/dart_api_impl.cc (right):

https://codereview.chromium.org/1182123002/diff/1/runtime/vm/dart_api_impl.cc...
runtime/vm/dart_api_impl.cc:3252: const Instance& data_obj =
Instance::Handle(TypedDataView::Data(view_obj));
Since isolate is available why not use
Instance::Handle(isolate, ...);

[Florian Schneider, 2015-06-12 16:41:12]

Committed patchset #2 (id:20001) manually as
19bb19d7162cfae8e9fc1981fc12d8c75a2f83b0 (presubmit successful).