Revert of Remove IPC::BrokerableAttachment.

ipc/ipc_channel_nacl.cc

Index: ipc/ipc_channel_nacl.cc
diff --git a/ipc/ipc_channel_nacl.cc b/ipc/ipc_channel_nacl.cc
index 0cea37315790f6fa767b88d63decdb51f7dff4ee..867eb97cb5ad5b65f373d5bb01fc94d10c56038c 100644
--- a/ipc/ipc_channel_nacl.cc
+++ b/ipc/ipc_channel_nacl.cc
@@ -23,7 +23,6 @@
 #include "ipc/ipc_listener.h"
 #include "ipc/ipc_logging.h"
 #include "ipc/ipc_message_attachment_set.h"
-#include "ipc/ipc_platform_file_attachment_posix.h"
 #include "native_client/src/public/imc_syscalls.h"
 #include "native_client/src/public/imc_types.h"
 
@@ -226,11 +225,8 @@
   data->swap(contents->data);
   read_queue_.push_back(data);
 
-  input_attachments_.reserve(contents->fds.size());
-  for (int fd : contents->fds) {
-    input_attachments_.push_back(
-        new internal::PlatformFileAttachment(base::ScopedFD(fd)));
-  }
+  input_fds_.insert(input_fds_.end(),
+                    contents->fds.begin(), contents->fds.end());
   contents->fds.clear();
 
   // In POSIX, we would be told when there are bytes to read by implementing
@@ -278,22 +274,16 @@
     linked_ptr<Message> msg = output_queue_.front();
     output_queue_.pop_front();
 
-    const size_t num_fds = msg->attachment_set()->size();
+    int fds[MessageAttachmentSet::kMaxDescriptorsPerMessage];
+    const size_t num_fds =
+        msg->attachment_set()->num_non_brokerable_attachments();
     DCHECK(num_fds <= MessageAttachmentSet::kMaxDescriptorsPerMessage);
-    std::vector<int> fds;
-    fds.reserve(num_fds);
-    for (size_t i = 0; i < num_fds; i++) {
-      scoped_refptr<MessageAttachment> attachment =
-          msg->attachment_set()->GetAttachmentAt(i);
-      DCHECK_EQ(MessageAttachment::Type::PLATFORM_FILE, attachment->GetType());
-      fds.push_back(static_cast<internal::PlatformFileAttachment&>(*attachment)
-                        .TakePlatformFile());
-    }
+    msg->attachment_set()->PeekDescriptors(fds);
 
     NaClAbiNaClImcMsgIoVec iov = {
       const_cast<void*>(msg->data()), msg->size()
     };
-    NaClAbiNaClImcMsgHdr msgh = {&iov, 1, fds.data(), num_fds};
+    NaClAbiNaClImcMsgHdr msgh = { &iov, 1, fds, num_fds };
     ssize_t bytes_written = imc_sendmsg(pipe_, &msgh, 0);
 
     DCHECK(bytes_written);  // The trusted side shouldn't return 0.
@@ -357,22 +347,23 @@
   return true;
 }
 
-bool ChannelNacl::GetAttachments(Message* msg) {
+bool ChannelNacl::GetNonBrokeredAttachments(Message* msg) {
   uint16_t header_fds = msg->header()->num_fds;
-  CHECK(header_fds == input_attachments_.size());
+  CHECK(header_fds == input_fds_.size());
   if (header_fds == 0)
     return true;  // Nothing to do.
 
-  for (auto& attachment : input_attachments_) {
-    msg->attachment_set()->AddAttachment(std::move(attachment));
-  }
-  input_attachments_.clear();
+  // The shenaniganery below with &foo.front() requires input_fds_ to have
+  // contiguous underlying storage (such as a simple array or a std::vector).
+  // This is why the header warns not to make input_fds_ a deque<>.
+  msg->attachment_set()->AddDescriptorsToOwn(&input_fds_.front(), header_fds);
+  input_fds_.clear();
   return true;
 }
 
 bool ChannelNacl::DidEmptyInputBuffers() {
-  // When the input data buffer is empty, the attachments should be too.
-  return input_attachments_.empty();
+  // When the input data buffer is empty, the fds should be too.
+  return input_fds_.empty();
 }
 
 void ChannelNacl::HandleInternalMessage(const Message& msg) {