Create core/html/media/ and move auxiliary media files in it.

third_party/WebKit/Source/core/core_idl_files.gni

 # Copyright 2016 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.
 
 import("//third_party/WebKit/Source/bindings/bindings.gni")
 import("//third_party/WebKit/Source/core/core.gni")
 
 # The paths in this file are absolute since this file is imported and the
 # file lists must be valid from multple "current directories".
 
@@ skipping 255 matching lines @@
                                  "html/HTMLTableElement.idl",
                                  "html/HTMLTableRowElement.idl",
                                  "html/HTMLTableSectionElement.idl",
                                  "html/HTMLTemplateElement.idl",
                                  "html/HTMLTextAreaElement.idl",
                                  "html/HTMLTitleElement.idl",
                                  "html/HTMLTrackElement.idl",
                                  "html/HTMLUListElement.idl",
                                  "html/HTMLUnknownElement.idl",
                                  "html/ImageData.idl",
-                                 "html/MediaError.idl",
                                  "html/RadioNodeList.idl",
                                  "html/TextMetrics.idl",
                                  "html/TimeRanges.idl",
                                  "html/ValidityState.idl",
                                  "html/VoidCallback.idl",
+                                 "html/media/MediaError.idl",
                                  "html/track/AudioTrackList.idl",
                                  "html/track/TextTrack.idl",
                                  "html/track/TextTrackCue.idl",
                                  "html/track/TextTrackCueList.idl",
                                  "html/track/TextTrackList.idl",
                                  "html/track/TrackEvent.idl",
                                  "html/track/VideoTrackList.idl",
                                  "html/track/vtt/VTTCue.idl",
                                  "html/track/vtt/VTTRegion.idl",
                                  "input/InputDeviceCapabilities.idl",
@@ skipping 360 matching lines @@
 core_generated_interface_idl_files = generated_webcore_testing_idl_files  # interfaces
 core_generated_dependency_idl_files =
     core_global_constructors_generated_idl_files  # partial interfaces
 
 # Dependency IDL files: don't generate individual bindings, but do process
 # in IDL dependency computation, and count as build dependencies
 # 'core_dependency_idl_files' is already used in Source/core, so avoid
 # collision
 core_all_dependency_idl_files =
     core_static_dependency_idl_files + core_generated_dependency_idl_files