Revert of Replace NPObject usage in ppapi with gin

Revert of Replace NPObject usage in ppapi with gin (patchset #27 of https://codereview.chromium.org/459553003/)

Reason for revert:
Failed memory tests:
http://build.chromium.org/p/chromium.memory/builders/Linux%20ASan%20LSan%20Tests%20%282%29/builds/6791

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

TBR=jochen@chromium.org,dmichael@chromium.org,kolczyk@opera.com
NOTREECHECKS=true
NOTRY=true
BUG=351636
Committed: https://crrev.com/a7c03d48cc9c256739fe4371237ac44dce37487e
Cr-Commit-Position: refs/heads/master@{#292574}

[raymes, 2014-08-29 05:04:26]

Created Revert of Replace NPObject usage in ppapi with gin

[commit-bot: I haz the power, 2014-08-29 05:05:33]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/raymes@chromium.org/522583002/1

[commit-bot: I haz the power, 2014-08-29 05:06:16]

Committed patchset #1 (id:1) as 9df0e049ce712a797facb9d9dc7e96eba103259d

[commit-bot: I haz the power, 2014-09-10 03:06:26]

Patchset 1 (id:??) landed as
https://crrev.com/a7c03d48cc9c256739fe4371237ac44dce37487e
Cr-Commit-Position: refs/heads/master@{#292574}