Clean up ChildProcessHost unique id generation.

content/public/browser/render_process_host.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_PUBLIC_BROWSER_RENDER_PROCESS_HOST_H_
 #define CONTENT_PUBLIC_BROWSER_RENDER_PROCESS_HOST_H_
 
 #include "base/basictypes.h"
 #include "base/id_map.h"
 #include "base/process/kill.h"
@@ skipping 138 matching lines @@
   // Returns whether this process is using the same StoragePartition as
   // |partition|.
   virtual bool InSameStoragePartition(StoragePartition* partition) const = 0;
 
   // Returns the unique ID for this child process host. This can be used later
   // in a call to FromID() to get back to this object (this is used to avoid
   // sending non-threadsafe pointers to other threads).
   //
   // This ID will be unique across all child process hosts, including workers,
   // plugins, etc.
+  //
+  // This will never return ChildProcessHost::kInvalidChildProcessUniqueId.
   virtual int GetID() const = 0;
 
   // Returns true iff channel_ has been set to non-NULL. Use this for checking
   // if there is connection or not. Virtual for mocking out for tests.
   virtual bool HasConnection() const = 0;
 
   // Call this to allow queueing of IPC messages that are sent before the
   // process is launched.
   virtual void EnableSendQueue() = 0;
 
@@ skipping 105 matching lines @@
   // module.
   static size_t GetMaxRendererProcessCount();
 
   static void RegisterRendererMainThreadFactory(
       RendererMainThreadFactoryFunction create);
 };
 
 }  // namespace content.
 
 #endif  // CONTENT_PUBLIC_BROWSER_RENDER_PROCESS_HOST_H_