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

ipc/ipc_channel_proxy.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 "base/bind.h"
 #include "base/compiler_specific.h"
 #include "base/debug/trace_event.h"
 #include "base/location.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 212 matching lines @@
   ipc_task_runner_->PostTask(
       FROM_HERE, base::Bind(&Context::OnAddFilter, this));
 }
 
 // Called on the listener's thread
 void ChannelProxy::Context::OnDispatchMessage(const Message& message) {
 #ifdef IPC_MESSAGE_LOG_ENABLED
   Logging* logger = Logging::GetInstance();
   std::string name;
   logger->GetMessageText(message.type(), &name, &message, NULL);
-  TRACE_EVENT1("task", "ChannelProxy::Context::OnDispatchMessage",
+  TRACE_EVENT1("toplevel", "ChannelProxy::Context::OnDispatchMessage",
                "name", name);
 #else
-  TRACE_EVENT2("task", "ChannelProxy::Context::OnDispatchMessage",
+  TRACE_EVENT2("toplevel", "ChannelProxy::Context::OnDispatchMessage",
                "class", IPC_MESSAGE_ID_CLASS(message.type()),
                "line", IPC_MESSAGE_ID_LINE(message.type()));
 #endif
 
   if (!listener_)
     return;
 
   OnDispatchConnected();
 
 #ifdef IPC_MESSAGE_LOG_ENABLED
@@ skipping 164 matching lines @@
   Channel* channel = context_.get()->channel_.get();
   // Channel must have been created first.
   DCHECK(channel) << context_.get()->channel_id_;
   return channel->GetPeerEuid(peer_euid);
 }
 #endif
 
 //-----------------------------------------------------------------------------
 
 }  // namespace IPC