[turbofan] Context specialization should only specialize loads/stores.

[turbofan] Context specialization should only specialize loads/stores.

The JSContextSpecialization should only care about loads from the
context and stores to the context, where the context is either a
HeapConstant or the special context Parameter (and a context for the
outer most function is provided). This way we don't eagerly embed
arbitrary context constants for no benefit, but we still specialize the
loads and store which we actually care about.

R=mstarzinger@chromium.org

Committed: https://crrev.com/443b071abe7e8480cb76c7a00346bc553dec5d5c
Cr-Commit-Position: refs/heads/master@{#29602}

[Benedikt Meurer, 2015-07-13 11:18:34]

bmeurer@chromium.org changed reviewers:
+ danno@chromium.org

[Benedikt Meurer, 2015-07-13 11:18:35]

Michi: PTAL
Danno: FYI

As discussed offline.

[Michael Starzinger, 2015-07-13 12:24:54]

LGTM.

[Benedikt Meurer, 2015-07-13 12:28:42]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2015-07-13 12:28:53]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1227963005/1

[commit-bot: I haz the power, 2015-07-13 12:30:55]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-07-13 12:31:08]

Patchset 1 (id:??) landed as
https://crrev.com/443b071abe7e8480cb76c7a00346bc553dec5d5c
Cr-Commit-Position: refs/heads/master@{#29602}