Move CompositionUnderlineVectorBuilder.* from web/ -> core/editing/.

third_party/WebKit/Source/core/editing/BUILD.gn

 # 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/core/core.gni")
 
 blink_core_sources("editing") {
   split_count = 5
   sources = [
     "CaretDisplayItemClient.cpp",
     "CaretDisplayItemClient.h",
     "CompositionUnderline.cpp",
     "CompositionUnderline.h",
+    "CompositionUnderlineVectorBuilder.cpp",
+    "CompositionUnderlineVectorBuilder.h",
     "DOMSelection.cpp",
     "DOMSelection.h",
     "DragCaret.cpp",
     "DragCaret.h",
     "EditingBehavior.cpp",
     "EditingBehavior.h",
     "EditingBehaviorTypes.h",
     "EditingBoundary.h",
     "EditingStrategy.cpp",
     "EditingStrategy.h",
@@ skipping 286 matching lines @@
     "//third_party/WebKit/Source:config",
     "//third_party/WebKit/Source:inside_blink",
   ]
 
   deps = [
     "//testing/gmock",
     "//testing/gtest",
     "//third_party/WebKit/Source/core:core",
   ]
 }