Revert a workaround commit for a Use-After-Free crash.

Revert a workaround commit r20158 for a Use-After-Free issue (http://crbug.com/244746) because a cleaner CL r207218 is landed.
URLRequestContext does not inherit SupportsWeakPtr now.

R=mmenke
BUG=244746

Review URL: https://chromiumcodereview.appspot.com/16870008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@207811 0039d316-1c4b-4281-b951-d872f2087c98
 void SocketStream::set_context(URLRequestContext* context) {
  const URLRequestContext* prev_context = context_;
 
  context_ = context;
 
   if (prev_context != context) {
     if (prev_context && pac_request_) {
      prev_context->proxy_service()->CancelPacRequest(pac_request_);
      pac_request_ = NULL;
    }

    net_log_.EndEvent(NetLog::TYPE_REQUEST_ALIVE);
    net_log_ = BoundNetLog();

    if (context) {
      net_log_ = BoundNetLog::Make(
          context->net_log(),
          NetLog::SOURCE_SOCKET_STREAM);

      net_log_.BeginEvent(NetLog::TYPE_REQUEST_ALIVE);
    }
  }
 }

 void SocketStream::set_context(URLRequestContext* context) {
  const URLRequestContext* prev_context = context_.get();
 
  if (context) {
    context_ = context->AsWeakPtr();
  } else {
    context_.reset();
  }
 
   if (prev_context != context) {
     if (prev_context && pac_request_) {
      prev_context->proxy_service()->CancelPacRequest(pac_request_);
      pac_request_ = NULL;
    }

    net_log_.EndEvent(NetLog::TYPE_REQUEST_ALIVE);
    net_log_ = BoundNetLog();

    if (context) {
      net_log_ = BoundNetLog::Make(
          context->net_log(),
          NetLog::SOURCE_SOCKET_STREAM);

      net_log_.BeginEvent(NetLog::TYPE_REQUEST_ALIVE);
    }
  }
 }
