Remove embedder custom elements.

sky/engine/public/BUILD.gn

 # Copyright 2014 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("//tools/grit/grit_rule.gni")
 
 group("test_support") {
   deps = [
     "//sky/engine/web:test_support",
   ]
@@ skipping 90 matching lines @@
     "web/Sky.h",
     "web/WebActiveWheelFlingParameters.h",
     "web/WebArrayBufferConverter.h",
     "web/WebArrayBufferView.h",
     "web/WebBeginFrameArgs.h",
     "web/WebCache.h",
     "web/WebCachedURLRequest.h",
     "web/WebCompositionUnderline.h",
     "web/WebConsoleMessage.h",
     "web/WebContentDetectionResult.h",
-    "web/WebCustomElement.h",
     "web/WebDocument.h",
     "web/WebElement.h",
     "web/WebExceptionCode.h",
     "web/WebFont.h",
     "web/WebFontDescription.h",
     "web/WebFrame.h",
     "web/WebFrameClient.h",
     "web/WebGlyphCache.h",
     "web/WebHitTestResult.h",
     "web/WebImageCache.h",
@@ skipping 30 matching lines @@
     "web/WebURLLoaderOptions.h",
     "web/WebUserGestureIndicator.h",
     "web/WebUserGestureToken.h",
     "web/WebView.h",
     "web/WebViewClient.h",
     "web/WebWidget.h",
     "web/WebWidgetClient.h",
     "web/linux/WebFontRendering.h",
   ]
 }