[DevTools] Cleanup DevToolsTarget and DevToolsManagerDelegate after moving to devtools_discovery.

content/content_browser.gypi

 # 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.
 
 {
   'dependencies': [
     '../base/base.gyp:base_static',
     '../crypto/crypto.gyp:crypto',
     '../device/vibration/vibration.gyp:device_vibration',
     '../device/vibration/vibration.gyp:device_vibration_mojo_bindings',
@@ skipping 95 matching lines @@
       'public/browser/cookie_store_factory.h',
       'public/browser/desktop_media_id.cc',
       'public/browser/desktop_media_id.h',
       'public/browser/desktop_notification_delegate.h',
       'public/browser/devtools_agent_host.h',
       'public/browser/devtools_agent_host_client.h',
       'public/browser/devtools_external_agent_proxy.h',
       'public/browser/devtools_external_agent_proxy_delegate.h',
       'public/browser/devtools_frontend_host.h',
       'public/browser/devtools_manager_delegate.h',
-      'public/browser/devtools_target.h',
       'public/browser/dom_operation_notification_details.h',
       'public/browser/dom_storage_context.h',
       'public/browser/download_danger_type.h',
       'public/browser/download_destination_observer.h',
       'public/browser/download_interrupt_reason_values.h',
       'public/browser/download_interrupt_reasons.h',
       'public/browser/download_item.h',
       'public/browser/download_manager.h',
       'public/browser/download_manager_delegate.cc',
       'public/browser/download_manager_delegate.h',
@@ skipping 1906 matching lines @@
         'browser/media/media_web_contents_observer.h',
       ],
     }],
     ['OS == "linux" and use_openssl==1', {
       'dependencies': [
         '../third_party/boringssl/boringssl.gyp:boringssl',
       ],
     }],
   ],
 }