Add Dart class for _ExternalUint8ClampedArray and API to allocate it.

Add Dart class for _ExternalUint8ClampedArray and API to allocate it.
Committed: https://code.google.com/p/dart/source/detail?r=17040

[siva, 2013-01-15 00:54:23]

lgtm

https://codereview.chromium.org/11881031/diff/4003/runtime/include/dart_api.h
File runtime/include/dart_api.h (right):

https://codereview.chromium.org/11881031/diff/4003/runtime/include/dart_api.h...
runtime/include/dart_api.h:1676: * 8-bit bytes.
Maybe we should also add a line here which explains what a clamped ByteArray is.

https://codereview.chromium.org/11881031/diff/4003/runtime/include/dart_api.h...
runtime/include/dart_api.h:1682: * \return The ByteArray object if no error
occurs. Otherwise returns
The clamped ByteArray object if

https://codereview.chromium.org/11881031/diff/4003/runtime/lib/byte_array.dart
File runtime/lib/byte_array.dart (right):

https://codereview.chromium.org/11881031/diff/4003/runtime/lib/byte_array.dar...
runtime/lib/byte_array.dart:1379: static const int _BYTES_PER_ELEMENT = 1;
Most of the code here is repeated both here and in _ExternalUint8Array. I am
wondering if we need a _ExternalUint8ArrayBase which extends _ByteArrayBase and
has all the methods but for 'operator[]' and 'operator[]='

[srdjan, 2013-01-15 01:11:10]

Thanks!

https://codereview.chromium.org/11881031/diff/4003/runtime/include/dart_api.h
File runtime/include/dart_api.h (right):

https://codereview.chromium.org/11881031/diff/4003/runtime/include/dart_api.h...
runtime/include/dart_api.h:1676: * 8-bit bytes.
On 2013/01/15 00:54:23, siva wrote:
> Maybe we should also add a line here which explains what a clamped ByteArray
is.

Done.

https://codereview.chromium.org/11881031/diff/4003/runtime/include/dart_api.h...
runtime/include/dart_api.h:1682: * \return The ByteArray object if no error
occurs. Otherwise returns
On 2013/01/15 00:54:23, siva wrote:
> The clamped ByteArray object if

Done.

https://codereview.chromium.org/11881031/diff/4003/runtime/lib/byte_array.dart
File runtime/lib/byte_array.dart (right):

https://codereview.chromium.org/11881031/diff/4003/runtime/lib/byte_array.dar...
runtime/lib/byte_array.dart:1379: static const int _BYTES_PER_ELEMENT = 1;
On 2013/01/15 00:54:23, siva wrote:
> Most of the code here is repeated both here and in _ExternalUint8Array. I am
> wondering if we need a _ExternalUint8ArrayBase which extends _ByteArrayBase
and
> has all the methods but for 'operator[]' and 'operator[]='

We've been through that already once :-) (. It does not work because of their
representation as VM objects.

[Anton Muhin, 2013-01-15 10:11:42]

https://codereview.chromium.org/11881031/diff/5013/runtime/include/dart_api.h
File runtime/include/dart_api.h (right):

https://codereview.chromium.org/11881031/diff/5013/runtime/include/dart_api.h...
runtime/include/dart_api.h:1688: DART_EXPORT Dart_Handle
Dart_NewExternalClampedByteArray(
It may be only me, but when I first time met the name Dart_NewExternalByteArray
I was 100% that it allocates an instance of ByteArray, not Uint8List.  May we
rename those methods?

Another issue: are you going to add eventually methods for all the array kinds? 
or maybe an ueber method taking kind as an argument.

Right now we've got in somewhat strange situation when some types can be
allocated directly while others cannot.

Surprisingly, to some extent it was better before as the only option one had was
to allocate Uint8List and then reuse its storage in some other view.