Remove WebMemoryUsageInfo, nothing uses it.

third_party/WebKit/public/blink_headers.gypi

 # Copyright 2015 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.
 
 {
   'variables': {
     'blink_public_sources': [
       "platform/Platform.h",
       "platform/WebApplicationCacheHost.h",
       "platform/WebApplicationCacheHostClient.h",
@@ skipping 407 matching lines @@
       "web/WebKit.h",
       "web/WebLabelElement.h",
       "web/WebLeakDetector.h",
       "web/WebLocalFrame.h",
       "web/WebMIDIClient.h",
       "web/WebMIDIPermissionRequest.h",
       "web/WebMeaningfulLayout.h",
       "web/WebMediaDevicesRequest.h",
       "web/WebMediaPlayerAction.h",
       "web/WebMediaStreamRegistry.h",
-      "web/WebMemoryUsageInfo.h",
       "web/WebMenuItemInfo.h",
       "web/WebNavigationPolicy.h",
       "web/WebNavigationType.h",
       "web/WebNavigatorContentUtilsClient.h",
       "web/WebNetworkStateNotifier.h",
       "web/WebNode.h",
       "web/WebNodeList.h",
       "web/WebOptionElement.h",
       "web/WebPagePopup.h",
       "web/WebPageSerializer.h",
@@ skipping 78 matching lines @@
       "web/WebWorkerContentSettingsClientProxy.h",
       "web/default/WebRenderTheme.h",
       "web/linux/WebFontRendering.h",
       "web/mac/WebScrollbarTheme.h",
       "web/mac/WebSubstringUtil.h",
       "web/modules/notifications/WebNotificationPermissionCallback.h",
       "web/win/WebFontRendering.h",
     ],
   },
 }