Make flow event traces disabled-by-default, and rename "ipc" and "task" categories to "toplevel"

ipc/ipc_sync_channel.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ipc/ipc_sync_channel.h"
 
 #include "base/bind.h"
 #include "base/debug/trace_event.h"
 #include "base/lazy_instance.h"
 #include "base/location.h"
@@ skipping 424 matching lines @@
 
 bool SyncChannel::Send(Message* message) {
   return SendWithTimeout(message, base::kNoTimeout);
 }
 
 bool SyncChannel::SendWithTimeout(Message* message, int timeout_ms) {
 #ifdef IPC_MESSAGE_LOG_ENABLED
   Logging* logger = Logging::GetInstance();
   std::string name;
   logger->GetMessageText(message->type(), &name, message, NULL);
-  TRACE_EVENT1("task", "SyncChannel::SendWithTimeout",
+  TRACE_EVENT1("toplevel", "SyncChannel::SendWithTimeout",
                "name", name);
 #else
-  TRACE_EVENT2("task", "SyncChannel::SendWithTimeout",
+  TRACE_EVENT2("toplevel", "SyncChannel::SendWithTimeout",
                "class", IPC_MESSAGE_ID_CLASS(message->type()),
                "line", IPC_MESSAGE_ID_LINE(message->type()));
 #endif
   if (!message->is_sync()) {
     ChannelProxy::Send(message);
     return true;
   }
 
   // *this* might get deleted in WaitForReply.
   scoped_refptr<SyncContext> context(sync_context());
@@ skipping 111 matching lines @@
   // manual reset since the object watcher might otherwise reset the event
   // when we're doing a WaitMany.
   dispatch_watcher_callback_ =
       base::Bind(&SyncChannel::OnWaitableEventSignaled,
                   base::Unretained(this));
   dispatch_watcher_.StartWatching(sync_context()->GetDispatchEvent(),
                                   dispatch_watcher_callback_);
 }
 
 }  // namespace IPC