Clean up ChildProcessHost unique id generation.

content/common/child_process_host_impl.h

 // 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.
 
 #ifndef CONTENT_COMMON_CHILD_PROCESS_HOST_IMPL_H_
 #define CONTENT_COMMON_CHILD_PROCESS_HOST_IMPL_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 19 matching lines @@
 class ChildProcessHostDelegate;
 
 // Provides common functionality for hosting a child process and processing IPC
 // messages between the host and the child process. Users are responsible
 // for the actual launching and terminating of the child processes.
 class CONTENT_EXPORT ChildProcessHostImpl : public ChildProcessHost,
                                             public IPC::Listener {
  public:
   virtual ~ChildProcessHostImpl();
 
-  // This value is guaranteed to never be returned by
-  // GenerateChildProcessUniqueId() below.
-  static int kInvalidChildProcessId;
-
   // Public and static for reuse by RenderMessageFilter.
   static void AllocateSharedMemory(
       size_t buffer_size, base::ProcessHandle child_process,
       base::SharedMemoryHandle* handle);
 
   // Returns a unique ID to identify a child process. On construction, this
   // function will be used to generate the id_, but it is also used to generate
   // IDs for the RenderProcessHost, which doesn't inherit from us, and whose IDs
   // must be unique for all child processes.
   //
   // This function is threadsafe since RenderProcessHost is on the UI thread,
   // but normally this will be used on the IO thread.
+  //
+  // This will never return ChildProcessHost::kInvalidUniqueID.
   static int GenerateChildProcessUniqueId();
 
   // ChildProcessHost implementation
   virtual bool Send(IPC::Message* message) OVERRIDE;
   virtual void ForceShutdown() OVERRIDE;
   virtual std::string CreateChannel() OVERRIDE;
   virtual bool IsChannelOpening() OVERRIDE;
   virtual void AddFilter(IPC::ChannelProxy::MessageFilter* filter) OVERRIDE;
 #if defined(OS_POSIX)
   virtual int TakeClientFileDescriptor() OVERRIDE;
@@ skipping 28 matching lines @@
   // thread, we don't have a IPC::ChannelProxy and so we manage filters
   // manually.
   std::vector<scoped_refptr<IPC::ChannelProxy::MessageFilter> > filters_;
 
   DISALLOW_COPY_AND_ASSIGN(ChildProcessHostImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_COMMON_CHILD_PROCESS_HOST_IMPL_H_