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

Review URL: https://codereview.chromium.org/522583002

Cr-Commit-Position: refs/heads/master@{#292574}

1 files changed, 0 insertions, 8 deletions

diff --git a/ppapi/tests/test_post_message.cc b/ppapi/tests/test_post_message.cc
index 6a415bb..5413b54 100644
--- a/ppapi/tests/test_post_message.cc
+++ b/ppapi/tests/test_post_message.cc
@@ -172,14 +172,6 @@ TestPostMessage::~TestPostMessage() {
 bool TestPostMessage::Init() {
   bool success = CheckTestingInterface();
 
-  // Add a post condition to tests which caches the postMessage function and
-  // then calls it after the instance is destroyed. The ensures that no UAF
-  // occurs because the MessageChannel may still be alive after the plugin
-  // instance is destroyed (it will get garbage collected eventually).
-  instance_->EvalScript("window.pluginPostMessage = "
-                        "document.getElementById('plugin').postMessage");
-  instance_->AddPostCondition("window.pluginPostMessage('') === undefined");
-
   // Set up a special listener that only responds to a FINISHED_WAITING string.
   // This is for use by WaitForMessages.
   std::string js_code;