Inline Array.shift() fast path instead of using a code stub.

Inline Array.shift() fast path instead of using a code stub.

TEST=mjsunit/array-shift,mjsunit/array-shift2,mjsunit/array-shift3
R=yangguo@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=21592

[Benedikt Meurer, 2014-06-02 06:36:50]

Simplifies code and gives small performance improvement for Array.shift() in
loops (i.e. Havlak).
PTAL

[Yang, 2014-06-02 06:57:01]

lgtm with comment.

https://codereview.chromium.org/308793010/diff/1/src/hydrogen.cc
File src/hydrogen.cc (right):

https://codereview.chromium.org/308793010/diff/1/src/hydrogen.cc#newcode7951
src/hydrogen.cc:7951: {
Could we have a BuildArrayShift instead of having the whole thing inside this
switch-case?

[Benedikt Meurer, 2014-06-02 07:02:11]

https://codereview.chromium.org/308793010/diff/1/src/hydrogen.cc
File src/hydrogen.cc (right):

https://codereview.chromium.org/308793010/diff/1/src/hydrogen.cc#newcode7951
src/hydrogen.cc:7951: {
As discussed offline: Leaving it here for consistency with the other array
builtins.

[Benedikt Meurer, 2014-06-02 07:02:46]

Committed patchset #1 manually as r21592 (presubmit successful).