Revert "Oilpan: Reduce the size of heap_page.h."

This reverts commit c4662e1ab59df9d91926eb4082dfc2fa3eb7d3e3.

Reason for revert:
This seems to gain the binary size by 0.3~0.9% on mac and win.

Original change's description:
> Oilpan: Reduce the size of heap_page.h.
> 
> heap_page.h is used in 6,000+ compilation units, and this CL reduces its
> estimated expanded size from 1.72MB to 1.40MB.
> 
> Bug: 242216
> Change-Id: I0f53c3f57511378289a841b89c6e01c4a2748d4a
> Reviewed-on: https://chromium-review.googlesource.com/1104080
> Reviewed-by: Keishi Hattori <keishi@chromium.org>
> Commit-Queue: Kent Tamura <tkent@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#567972}

TBR=keishi@chromium.org,tkent@chromium.org

Change-Id: I54c95f8102aadf8459a833db0d27b970d291eb93
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 242216, 853703
Reviewed-on: https://chromium-review.googlesource.com/1104357
Reviewed-by: Taiju Tsuiki <tzik@chromium.org>
Commit-Queue: Taiju Tsuiki <tzik@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567981}
2 files changed