Small polishing changes to the native js.

Small polishing changes to the native js.

R=jkummerow@chromium.org

Committed: https://crrev.com/42415bf9bc5aa7266267e731140e5beed6909796
Cr-Commit-Position: refs/heads/master@{#27949}

[Jakob Kummerow, 2015-04-20 15:21:54]

lgtm

[Yang, 2015-04-20 18:18:02]

The CQ bit was checked by yangguo@chromium.org

[commit-bot: I haz the power, 2015-04-20 18:18:19]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1096763003/1

[commit-bot: I haz the power, 2015-04-20 19:19:01]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-20 19:19:14]

Patchset 1 (id:??) landed as
https://crrev.com/42415bf9bc5aa7266267e731140e5beed6909796
Cr-Commit-Position: refs/heads/master@{#27949}

[dusmil.imgtec, 2015-04-21 12:23:30]

The removal of GetRootNan() causes problems for MIPS. The mips have different
qNan encoding.

We rely on GetRootNan() so the NaNs dumped in snapshot are unified and come from
the same source which is global nan.
Doing so we can change Nan to be consistent to MIPS spec during deserialization
by patching global nan.

See line isolate.cc:2167

  // Quiet the heap NaN if needed on target platform.
  if (!create_heap_objects) Assembler::QuietNaN(heap_.nan_value());


The 0/0 expression will create x86 NaNs (wrong values for mips) during snapshot
creation of builtins on host which are scattered and placed in snapshot
so they cannot longer be fixed during bootstrap.