Added following dart API changes to enable more efficient access based

Added following dart API changes to enable more efficient access based
on the dartium usage pattern:
- Dart_GetNativeStringArgument (gets a String object, peer etc. directly from
  the native arguments)
- Dart_SetWeakHandleReturnValue (allows a weak handle to be passed to the
  return value, this ensures a new local handle does not have to be created
  from a weak handle just to return a value)
- Dart_StringGetProperties (gets some common properties of a string, avoids
  multiple API calls to set up a native string)

R=srdjan@google.com, vsm@google.com

Committed: https://code.google.com/p/dart/source/detail?r=26046

[vsm, 2013-08-12 17:59:04]

lgtm

https://chromiumcodereview.appspot.com/22632010/diff/1/runtime/vm/dart_api_im...
File runtime/vm/dart_api_impl.cc (right):

https://chromiumcodereview.appspot.com/22632010/diff/1/runtime/vm/dart_api_im...
runtime/vm/dart_api_impl.cc:1859: const String& str =
Api::UnwrapStringHandle(isolate, object);
Do you need some error checking if the object is not a string or is null?  Looks
like this always returns Success.

[srdjan, 2013-08-12 18:09:57]

LGTM

https://codereview.chromium.org/22632010/diff/1/runtime/vm/dart_api_impl.cc
File runtime/vm/dart_api_impl.cc (right):

https://codereview.chromium.org/22632010/diff/1/runtime/vm/dart_api_impl.cc#n...
runtime/vm/dart_api_impl.cc:1862: ASSERT(*peer != 0);
Should this be 0 or NULL? (also below).

https://codereview.chromium.org/22632010/diff/1/runtime/vm/dart_api_impl.cc#n...
runtime/vm/dart_api_impl.cc:3694: ASSERT(*peer != 0);
ditto?

https://codereview.chromium.org/22632010/diff/1/runtime/vm/dart_api_impl.cc#n...
runtime/vm/dart_api_impl.cc:3697: *peer = 0;
ditto

[siva, 2013-08-13 01:19:09]

https://chromiumcodereview.appspot.com/22632010/diff/1/runtime/vm/dart_api_im...
File runtime/vm/dart_api_impl.cc (right):

https://chromiumcodereview.appspot.com/22632010/diff/1/runtime/vm/dart_api_im...
runtime/vm/dart_api_impl.cc:1859: const String& str =
Api::UnwrapStringHandle(isolate, object);
On 2013/08/12 17:59:04, vsm wrote:
> Do you need some error checking if the object is not a string or is null? 
Looks
> like this always returns Success.

Done.

https://chromiumcodereview.appspot.com/22632010/diff/1/runtime/vm/dart_api_im...
runtime/vm/dart_api_impl.cc:1862: ASSERT(*peer != 0);
On 2013/08/12 18:09:57, srdjan wrote:
> Should this be 0 or NULL? (also below).

Done.

https://chromiumcodereview.appspot.com/22632010/diff/1/runtime/vm/dart_api_im...
runtime/vm/dart_api_impl.cc:3694: ASSERT(*peer != 0);
On 2013/08/12 18:09:57, srdjan wrote:
> ditto?

Done.

https://chromiumcodereview.appspot.com/22632010/diff/1/runtime/vm/dart_api_im...
runtime/vm/dart_api_impl.cc:3697: *peer = 0;
On 2013/08/12 18:09:57, srdjan wrote:
> ditto

Done.

[siva, 2013-08-13 01:19:33]

Committed patchset #2 manually as r26046 (presubmit successful).