Revert of "Prevent race conditions between decrypt and close session"

[ Original CL http://ag/3890635,
  Merge of http://go/wvgerrit/50340 ]

The original fix was not sufficient to address all race conditions.
A subsequent CL will address them.

Bug: 73781703
Bug: 79158083
Bug: 79262108
Test: WV unit/integration tests, GTS GtsMediaTestCases tests and
      24 hours of continuous Netflix playback.

Change-Id: I869c22a250e2467b3d49935815e4157dc012fff5

libwvdrmengine/cdm/core/src/cdm_session.cpp

@@ -72,11 +72,6 @@ CdmSession::~CdmSession() {
   }
 }
 
-void CdmSession::Close() {
-  AutoLock lock(close_lock_);
-  closed_ = true;
-}
-
 CdmResponseType CdmSession::Init(
     CdmClientPropertySet* cdm_client_property_set) {
   return Init(cdm_client_property_set, NULL, NULL);
@@ -581,11 +576,6 @@ CdmResponseType CdmSession::Decrypt(const CdmDecryptionParameters& params) {
     return NOT_INITIALIZED_ERROR;
   }
 
-  AutoLock lock(close_lock_);
-  if (IsClosed()) {
-    return SESSION_CLOSED_1;
-  }
-
   // Playback may not begin until either the start time passes or the license
   // is updated, so we treat this Decrypt call as invalid.
   if (params.is_encrypted) {