Allow String.fromCharCodes to work directly on a GrowableObjectArray.

Allow String.fromCharCodes to work directly on a GrowableObjectArray.

Avoids copying the data from the internal ObjectArray into a new
ObjectArray before creating the string.

Committed: https://code.google.com/p/dart/source/detail?r=20060

[Lasse Reichstein Nielsen, 2013-03-14 15:34:24]

It seems calling String.fromCharCodes with a growable list is a common case, so
this should avoid at least some of the overhead.

[siva, 2013-03-14 15:56:02]

lgtm

https://codereview.chromium.org/12632014/diff/1/runtime/lib/string.cc
File runtime/lib/string.cc (right):

https://codereview.chromium.org/12632014/diff/1/runtime/lib/string.cc#newcode28
runtime/lib/string.cc:28: : a.Length();
I would structure this code as:
if (!list.IsGrowableObjectArray() && ! list.IsArray()) {
  ...
  ...
}
Array& a = Array::Handle();
intptr_t array_len = 0;
if (list.IsGrowableObjectArray()) {
  const GrowableObjectArray& ga = GrowableObjectArray::Cast(list);
  a ^= ga.data();
  array_len = ga.Length();
} else {
  a ^= Array::Cast(list).raw();
  array_length = a.Length();
}
....
....

https://codereview.chromium.org/12632014/diff/1/runtime/lib/string.cc#newcode62
runtime/lib/string.cc:62: 
Why remove the blank line here, we normally have 2 blank lines after a function.

[Lasse Reichstein Nielsen, 2013-03-15 06:58:40]

https://codereview.chromium.org/12632014/diff/1/runtime/lib/string.cc
File runtime/lib/string.cc (right):

https://codereview.chromium.org/12632014/diff/1/runtime/lib/string.cc#newcode28
runtime/lib/string.cc:28: : a.Length();
Much better. Done!

https://codereview.chromium.org/12632014/diff/1/runtime/lib/string.cc#newcode62
runtime/lib/string.cc:62: 
No reason. I moved the body of the method into a helper function at some point,
and then back again. Must have lost a line along the way.

[Lasse Reichstein Nielsen, 2013-03-15 07:22:22]

Committed patchset #2 manually as r20060 (presubmit successful).