Remove IPC::BrokerableAttachment.

ipc/ipc_send_fds_test.cc

Index: ipc/ipc_send_fds_test.cc
diff --git a/ipc/ipc_send_fds_test.cc b/ipc/ipc_send_fds_test.cc
index f648b6411ab27c9c6e150f700e89adb00949feb6..3c814bb165d5f60a44a5fff02c5149698654d732 100644
--- a/ipc/ipc_send_fds_test.cc
+++ b/ipc/ipc_send_fds_test.cc
@@ -77,8 +77,8 @@ class MyChannelDescriptorListener : public MyChannelDescriptorListenerBase {
         num_fds_received_(0) {
   }
 
-  bool GotExpectedNumberOfDescriptors() const {
-    return num_fds_received_ == kNumFDsToSend * kNumMessages;
+  unsigned num_fds_received() const {
+    return num_fds_received_;
   }
 
   void OnChannelError() override {
@@ -163,7 +163,7 @@ class SendFdsTestClientFixture : public IpcChannelMojoTestClient {
 
     // Verify that the message loop was exited due to getting the correct number
     // of descriptors, and not because of the channel closing unexpectedly.
-    EXPECT_TRUE(listener.GotExpectedNumberOfDescriptors());
+    EXPECT_EQ(kNumFDsToSend * kNumMessages, listener.num_fds_received());
 
     Close();
   }