Add UMA reports for Linux nacl_helper startup status

content/common/zygote_fork_delegate_linux.h

 // Copyright (c) 2011 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_ZYGOTE_FORK_DELEGATE_LINUX_H_
 #define CONTENT_COMMON_ZYGOTE_FORK_DELEGATE_LINUX_H_
 #pragma once
 
 #include <unistd.h>
 
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
 
 // The ZygoteForkDelegate allows the Chrome Linux zygote to delegate
 // fork operations to another class that knows how to do some
 // specialized version of fork.
 class ZygoteForkDelegate {
  public:
   // A ZygoteForkDelegate is created during Chrome linux zygote
-  // initialization, and provides "fork()" functionality with
-  // as an alternative to forking the zygote. A new delegate is
-  // passed in as an argument to ZygoteMain().
+  // initialization, and provides "fork()" functionality as an
+  // alternative to forking the zygote.  A new delegate is passed in
+  // as an argument to ZygoteMain().
   ZygoteForkDelegate() {}
   virtual ~ZygoteForkDelegate() {}
 
   // Initialization happens in the zygote after it has been
   // started by ZygoteMain.
   virtual void Init(bool sandboxed,
                     int browserdesc,
                     int sandboxdesc) = 0;
 
-  // Returns 'true' if the delegate would like to handle a given
-  // fork request. Otherwise returns false.
-  virtual bool CanHelp(const std::string& process_type) = 0;
+  // After Init, supply a UMA_HISTOGRAM_ENUMERATION the delegate
+  // would like to have done on the first fork.

[agl, 2011/10/19 16:17:27]

s/have done/supply/ ?

[Roland McGrath, 2011/10/19 18:34:15]

Done.

+  virtual void InitialUMA(std::string* uma_name,
+                          int* uma_sample,
+                          int* uma_boundary_value) = 0;
+
+  // Returns 'true' if the delegate would like to handle a given fork
+  // request.  Otherwise returns false.  Optionally, fills in uma_name et al
+  // with a report the helper wants to make via UMA_HISTOGRAM_ENUMERATION.
+  virtual bool CanHelp(const std::string& process_type, std::string* uma_name,
+                       int* uma_sample, int* uma_boundary_value) = 0;
 
   // Delegate forks, returning a -1 on failure. Outside the
   // suid sandbox, Fork() returns the Linux process ID. Inside
   // the sandbox, returns a positive integer, with PID discovery
   // handled by the sandbox.
   virtual pid_t Fork(const std::vector<int>& fds) = 0;
 
   // After a successful for, signal the child to indicate that
   // the child's PID has been received. Also communicate the
   // channel switch as a part of acknowledgement message.
   virtual bool AckChild(int fd, const std::string& channel_switch) = 0;
 };
 #endif  // CONTENT_COMMON_ZYGOTE_FORK_DELEGATE_LINUX_H_