Revert of Replace NPObject usage in ppapi with gin

Revert of Replace NPObject usage in ppapi with gin (patchset #28 id:540001 of https://codereview.chromium.org/459553003/)

Reason for revert:
Causing a bunch of top crashes:
go/crash/c383c0c43c093ea1
go/crash/576a27ecf5f32094
go/crash/08fc74881d1819ac
go/crash/a6a00150ba55c0bf


Original issue's description:
> Replace NPObject usage in ppapi with gin
> 
> This replaces usage of NPObject in pepper with gin-backed V8 objects. It is unfortunate that this CL is so large, but there isn't a nice way to have the old implementation and the new one side-by-side. 
> 
> There are 4 major parts to this CL:
> 1) Changing the HostVarTracker to track V8ObjectVars rather than NPObjectVars (host_var_tracker.cc).
> 2) Changing plugin elements (in plugin_object.cc) to be gin-backed objects. 
> 3) Changing postMessage bindings (message_channel.cc) be gin-backed objects.
> 4) Changing the implementation of PPB_Var_Deprecated (ppb_var_deprecated_impl.cc) to call directly into V8.
> 
> 
> BUG=351636
> 
> Committed: https://chromium.googlesource.com/chromium/src/+/21f446ae855d60cc896b40cb9a3249ed07f150b3
> 
> Committed: https://chromium.googlesource.com/chromium/src/+/ee49e63baf57e503bd71dfe61c8a80df63eac9aa
> 
> Committed: https://chromium.googlesource.com/chromium/src/+/e06bc5d896e494b9ec556f0e89dcc523778a1432

TBR=jochen@chromium.org,dmichael@chromium.org,kolczyk@opera.com
NOTREECHECKS=true
NOTRY=true
BUG=351636
Committed: https://crrev.com/dc463a9f84db834c51feff23aa46e41dad33c6ff
Cr-Commit-Position: refs/heads/master@{#293079}

[raymes, 2014-09-03 05:47:32]

Created Revert of Replace NPObject usage in ppapi with gin

[commit-bot: I haz the power, 2014-09-03 05:48:57]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/raymes@chromium.org/537483002/1

[commit-bot: I haz the power, 2014-09-03 05:52:08]

Committed patchset #1 (id:1) as de1a0571675f745b1f316974728507ce5c15144d

[commit-bot: I haz the power, 2014-09-10 03:23:48]

Patchset 1 (id:??) landed as
https://crrev.com/dc463a9f84db834c51feff23aa46e41dad33c6ff
Cr-Commit-Position: refs/heads/master@{#293079}