Optimize concatenation of lists of onebyte strings by implementing it in Dart.

Optimize concatenation of lists of onebyte strings by implementing it in Dart.

R=asiva@google.com

Committed: https://code.google.com/p/dart/source/detail?r=22532

[siva, 2013-05-06 23:08:49]

lgtm

https://codereview.chromium.org/14820013/diff/3001/runtime/lib/string_patch.dart
File runtime/lib/string_patch.dart (right):

https://codereview.chromium.org/14820013/diff/3001/runtime/lib/string_patch.d...
runtime/lib/string_patch.dart:348: totalLength += s.length;
The totalLength addition could be done under an else right, as it is not needed
for the non OneByteString case.
if (s is! _OneByteString) {
  ..
} else {
  totalLength += ...
}

https://codereview.chromium.org/14820013/diff/3001/runtime/lib/string_patch.d...
runtime/lib/string_patch.dart:462: return _concatAll(stringsArray);
Why not have a isOneByteString flag which is set in the loop above and directly
dispatch to 
_OneByteString._concatAll(....) or
_concatAllNative(...)
like how you do in _interpolate above.

https://codereview.chromium.org/14820013/diff/3001/runtime/lib/string_patch.d...
runtime/lib/string_patch.dart:473: totalLength += e.length;
Ditto comment about totalLength under an else.

[srdjan, 2013-05-08 21:17:21]

Also, for performance reasons, limited the size that can be handled  inside Dart
to 128 until we generate better code (we must unbox index and value).

https://codereview.chromium.org/14820013/diff/3001/runtime/lib/string_patch.dart
File runtime/lib/string_patch.dart (right):

https://codereview.chromium.org/14820013/diff/3001/runtime/lib/string_patch.d...
runtime/lib/string_patch.dart:348: totalLength += s.length;
On 2013/05/06 23:08:49, siva wrote:
> The totalLength addition could be done under an else right, as it is not
needed
> for the non OneByteString case.
> if (s is! _OneByteString) {
>   ..
> } else {
>   totalLength += ...
> }

Done.

https://codereview.chromium.org/14820013/diff/3001/runtime/lib/string_patch.d...
runtime/lib/string_patch.dart:473: totalLength += e.length;
On 2013/05/06 23:08:49, siva wrote:
> Ditto comment about totalLength under an else.

Here it is different since we stop looping the first time we recognize that it
is not a oneByteString.

[srdjan, 2013-05-08 21:33:07]

Committed patchset #5 manually as r22532 (presubmit successful).