IPC: Add attachment brokering support to the message header.

Message dispatch happens before message translation, and message dispatch
requires that all brokered attachments have been received. This means that
attachment brokering needs to function without message translation. This is
accomplished by modifying the message header to include a new field
num_brokered_attachments, and writing the attachment ids into the IPC Channel
immediately following the pickled message itself.

AttachmentBrokerPrivilegedWinUnittest was expanded to test ChannelReader in the
receiving process. It is now a fully functional end-to-end test of attachment
brokering.

BUG=493414

Review URL: https://codereview.chromium.org/1286253002

Cr-Commit-Position: refs/heads/master@{#344389}

1 files changed, 21 insertions, 11 deletions

diff --git a/ipc/ipc_channel_reader.cc b/ipc/ipc_channel_reader.cc
index a76b7e6..c47d2bc 100644
--- a/ipc/ipc_channel_reader.cc
+++ b/ipc/ipc_channel_reader.cc
@@ -20,8 +20,7 @@ ChannelReader::ChannelReader(Listener* listener) : listener_(listener) {
 }
 
 ChannelReader::~ChannelReader() {
-  if (!blocked_ids_.empty())
-    StopObservingAttachmentBroker();
+  DCHECK(blocked_ids_.empty());
 }
 
 ChannelReader::DispatchState ChannelReader::ProcessIncomingMessages() {
@@ -85,11 +84,14 @@ bool ChannelReader::TranslateInputData(const char* input_data,
 
   // Dispatch all complete messages in the data buffer.
   while (p < end) {
-    const char* message_tail = Message::FindNext(p, end);
-    if (message_tail) {
-      int len = static_cast<int>(message_tail - p);
+    Message::NextMessageInfo info = Message::FindNext(p, end);
+    if (info.message_found) {
+      int pickle_len = static_cast<int>(info.pickle_end - p);
+      Message translated_message(p, pickle_len);
+
+      for (const auto& id : info.attachment_ids)
+        translated_message.AddPlaceholderBrokerableAttachmentWithId(id);
 
-      Message translated_message(p, len);
       if (!GetNonBrokeredAttachments(&translated_message))
         return false;
 
@@ -103,7 +105,7 @@ bool ChannelReader::TranslateInputData(const char* input_data,
         if (blocked_ids.empty()) {
           // Dispatch the message and continue the loop.
           DispatchMessage(&translated_message);
-          p = message_tail;
+          p = info.message_end;
           continue;
         }
 
@@ -114,7 +116,7 @@ bool ChannelReader::TranslateInputData(const char* input_data,
       // Make a deep copy of |translated_message| to add to the queue.
       scoped_ptr<Message> m(new Message(translated_message));
       queued_messages_.push_back(m.release());
-      p = message_tail;
+      p = info.message_end;
     } else {
       // Last message is partial.
       break;
@@ -149,6 +151,13 @@ ChannelReader::DispatchState ChannelReader::DispatchMessages() {
   return DISPATCH_FINISHED;
 }
 
+void ChannelReader::CleanUp() {
+  if (!blocked_ids_.empty()) {
+    StopObservingAttachmentBroker();
+    blocked_ids_.clear();
+  }
+}
+
 void ChannelReader::DispatchMessage(Message* m) {
   m->set_sender_pid(GetSenderPID());
 
@@ -191,8 +200,9 @@ ChannelReader::AttachmentIdSet ChannelReader::GetBrokeredAttachments(
 
 #if USE_ATTACHMENT_BROKER
   MessageAttachmentSet* set = msg->attachment_set();
-  for (const scoped_refptr<BrokerableAttachment>& attachment :
-       set->GetBrokerableAttachmentsForUpdating()) {
+  std::vector<const BrokerableAttachment*> brokerable_attachments_copy =
+      set->PeekBrokerableAttachments();
+  for (const BrokerableAttachment* attachment : brokerable_attachments_copy) {
     if (attachment->NeedsBrokering()) {
       AttachmentBroker* broker = GetAttachmentBroker();
       scoped_refptr<BrokerableAttachment> brokered_attachment;
@@ -203,7 +213,7 @@ ChannelReader::AttachmentIdSet ChannelReader::GetBrokeredAttachments(
         continue;
       }
 
-      attachment->PopulateWithAttachment(brokered_attachment.get());
+      set->ReplacePlaceholderWithAttachment(brokered_attachment);
     }
   }
 #endif  // USE_ATTACHMENT_BROKER