Update ChannelReader to use AttachmentBroker.

Previously, translating from bytes into messages and dispatching the messages
was accomplished in a single step. I've split this into two steps. The function
TranslateInputData turns bytes into messages, and puts those messages in a
queue. The function DispatchMessages() dispatches messages from the queue.
Messages cannot be dispatched until all attachments have been brokered, so
DispatchMessages() will sometimes wait (asynchronously) for the attachments to
get brokered.

BUG=466437

Review URL: https://codereview.chromium.org/1206093002

Cr-Commit-Position: refs/heads/master@{#340509}

1 files changed, 13 insertions, 0 deletions

diff --git a/ipc/ipc_message_attachment_set.cc b/ipc/ipc_message_attachment_set.cc
index ed653f3..1a4969f 100644
--- a/ipc/ipc_message_attachment_set.cc
+++ b/ipc/ipc_message_attachment_set.cc
@@ -143,6 +143,19 @@ MessageAttachmentSet::PeekBrokerableAttachments() const {
   return output;
 }
 
+std::vector<scoped_refptr<BrokerableAttachment>>
+MessageAttachmentSet::GetBrokerableAttachmentsForUpdating() {
+  std::vector<scoped_refptr<BrokerableAttachment>> output;
+  for (const scoped_refptr<MessageAttachment>& attachment : attachments_) {
+    if (attachment->GetType() ==
+        MessageAttachment::TYPE_BROKERABLE_ATTACHMENT) {
+      output.push_back(scoped_refptr<BrokerableAttachment>(
+          static_cast<BrokerableAttachment*>(attachment.get())));
+    }
+  }
+  return output;
+}
+
 #if defined(OS_POSIX)
 
 void MessageAttachmentSet::PeekDescriptors(base::PlatformFile* buffer) const {