Don't report 'custom' processes as untracked.

content/browser/browser_child_process_host_impl.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 "content/browser/browser_child_process_host_impl.h"
 
 #include "base/base_switches.h"
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/debug/alias.h"
@@ skipping 481 matching lines @@
       memory_size = 64 << 10;  // 64 KiB
       metrics_name = "PpapiPluginMetrics";
       break;
 
     case PROCESS_TYPE_PPAPI_BROKER:
       memory_size = 64 << 10;  // 64 KiB
       metrics_name = "PpapiBrokerMetrics";
       break;
 
     default:
-      UMA_HISTOGRAM_ENUMERATION(
-          "UMA.SubprocessMetricsProvider.UntrackedProcesses",
-          data_.process_type, PROCESS_TYPE_CONTENT_END);
+      // Report new processes. "Custom" ones are renumbered to 1000+ so that
+      // they won't conflict with any standard ones in the future.
+      int process_type = data_.process_type;
+      if (process_type >= PROCESS_TYPE_CONTENT_END)
+        process_type += 1000 - PROCESS_TYPE_CONTENT_END;
+      UMA_HISTOGRAM_SPARSE_SLOWLY(
+          "UMA.SubprocessMetricsProvider.UntrackedProcesses", process_type);
       return;
   }
 
   // Create the shared memory segment and attach an allocator to it.
   // Mapping the memory shouldn't fail but be safe if it does; everything
   // will continue to work but just as if persistence weren't available.
   std::unique_ptr<base::SharedMemory> shm(new base::SharedMemory());
   if (!shm->CreateAndMapAnonymous(memory_size))
     return;
   metrics_allocator_.reset(new base::SharedPersistentMemoryAllocator(
@@ skipping 82 matching lines @@
 
 #if defined(OS_WIN)
 
 void BrowserChildProcessHostImpl::OnObjectSignaled(HANDLE object) {
   OnChildDisconnected();
 }
 
 #endif
 
 }  // namespace content