Don't make classes derive from ChildProcessHost, and instead have them use it through composition...

content/content_common.gypi

 # 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.
 
 {
   'dependencies': [
     '../base/base.gyp:base',
     '../build/temp_gyp/googleurl.gyp:googleurl',
     '../gpu/gpu.gyp:gpu_ipc',
     '../ipc/ipc.gyp:ipc',
@@ skipping 11 matching lines @@
     '../webkit/support/webkit_support.gyp:fileapi',
   ],
   'include_dirs': [
     '..',
   ],
   'export_dependent_settings': [
     '../base/base.gyp:base',
   ],
   'sources': [
     'public/common/bindings_policy.h',
+    'public/common/child_process_host_delegate.h',
     'public/common/child_process_sandbox_support_linux.h',
     'public/common/content_constants.cc',
     'public/common/content_constants.h',
     'public/common/content_paths.h',
     'public/common/content_restriction.h',
     'public/common/content_switches.cc',
     'public/common/content_switches.h',
     'public/common/dx_diag_node.cc',
     'public/common/dx_diag_node.h',
     'public/common/file_chooser_params.cc',
@@ skipping 275 matching lines @@
       ],
       'link_settings': {
         'libraries': [
           '-lEGL',
           '-lGLESv2',
         ],
       },
     }],
   ],
 }