Replace collectLayerFragments() with FragmentainerIterator.

third_party/WebKit/Source/core/layout/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("layout") {
   split_count = 5
 
   sources = [
     "BidiRun.h",
     "BidiRunForLine.cpp",
     "BidiRunForLine.h",
     "ClipRect.cpp",
     "ClipRect.h",
     "ClipRects.h",
     "ClipRectsCache.h",
     "ColumnBalancer.cpp",
     "ColumnBalancer.h",
     "CounterNode.cpp",
     "CounterNode.h",
     "DepthOrderedLayoutObjectList.cpp",
     "DepthOrderedLayoutObjectList.h",
     "FloatingObjects.cpp",
     "FloatingObjects.h",
+    "FragmentainerIterator.cpp",
+    "FragmentainerIterator.h",
     "FragmentationContext.h",
     "GeneratedChildren.h",
     "HitTestCache.cpp",
     "HitTestCache.h",
     "HitTestCanvasResult.cpp",
     "HitTestLocation.cpp",
     "HitTestLocation.h",
     "HitTestResult.cpp",
     "HitTestingTransformState.cpp",
     "HitTestingTransformState.h",
@@ skipping 316 matching lines @@
       "LayoutThemeAndroid.cpp",
       "LayoutThemeAndroid.h",
     ]
   }
 
   configs += [
     # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
     "//build/config/compiler:no_size_t_to_int_warning",
   ]
 }