Remove WebWaitableEvent and replace it with WaitableEvent.

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/URLConversion.h",
       "platform/WebApiKeyValidator.h",
@@ skipping 215 matching lines @@
       "platform/WebTransformOperations.h",
       "platform/WebURL.h",
       "platform/WebURLError.h",
       "platform/WebURLLoadTiming.h",
       "platform/WebURLLoader.h",
       "platform/WebURLLoaderClient.h",
       "platform/WebURLRequest.h",
       "platform/WebURLResponse.h",
       "platform/WebUnitTestSupport.h",
       "platform/WebVector.h",
-      "platform/WebWaitableEvent.h",
       "platform/linux/WebFallbackFont.h",
       "platform/linux/WebFontInfo.h",
       "platform/linux/WebFontRenderStyle.h",
       "platform/linux/WebSandboxSupport.h",
       "platform/mac/WebSandboxSupport.h",
       "platform/modules/app_banner/WebAppBannerClient.h",
       "platform/modules/app_banner/WebAppBannerPromptReply.h",
       "platform/modules/app_banner/WebAppBannerPromptResult.h",
       "platform/modules/background_sync/WebSyncClient.h",
       "platform/modules/background_sync/WebSyncError.h",
@@ skipping 273 matching lines @@
       "web/modules/serviceworker/WebServiceWorkerContextClient.h",
       "web/modules/serviceworker/WebServiceWorkerContextProxy.h",
       "web/modules/serviceworker/WebServiceWorkerNetworkProvider.h",
       "web/modules/webmidi/WebMIDIClient.h",
       "web/modules/webmidi/WebMIDIOptions.h",
       "web/modules/webmidi/WebMIDIPermissionRequest.h",
       "web/win/WebFontRendering.h",
     ],
   },
 }