[x86] Improve code generation for context materialization.

[x86] Improve code generation for context materialization.

On Intel targets, it is cheaper to load the context from the frame
instead of loading the context as a constant (which usually involves a
PropertyCell because the context is in new space when we compile the
function).

R=jarin@chromium.org

Committed: https://crrev.com/502898ef60f011e3d4150cac8815c001928d6a26
Cr-Commit-Position: refs/heads/master@{#26935}

[Benedikt Meurer, 2015-03-02 07:39:22]

PTAL

[Jarin, 2015-03-02 08:15:41]

lgtm

[Benedikt Meurer, 2015-03-02 08:21:48]

The CQ bit was checked by bmeurer@chromium.org

[Benedikt Meurer, 2015-03-02 08:21:48]

The patchset sent to the CQ was uploaded after l-g-t-m from jarin@chromium.org
Link to the patchset: https://codereview.chromium.org/970803002/#ps20001 (title:
"Fix ia32.")

[commit-bot: I haz the power, 2015-03-02 08:22:13]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/970803002/20001

[Benedikt Meurer, 2015-03-02 09:09:48]

Committed patchset #2 (id:20001) manually as
502898ef60f011e3d4150cac8815c001928d6a26 (presubmit successful).

[commit-bot: I haz the power, 2015-03-02 09:09:52]

Patchset 2 (id:??) landed as
https://crrev.com/502898ef60f011e3d4150cac8815c001928d6a26
Cr-Commit-Position: refs/heads/master@{#26935}