Remove platform/CheckedInt.h, we can use wtf/CheckedNumeric.h instead.

third_party/WebKit/Source/platform/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("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//testing/libfuzzer/fuzzer_test.gni")
 import("//testing/test.gni")
 import("//third_party/WebKit/Source/build/scripts/scripts.gni")
 import("//third_party/WebKit/Source/config.gni")
@@ skipping 185 matching lines @@
   visibility = [
     "//third_party/WebKit/*",
     "//url/mojo:url_mojom_origin_blink_cpp_sources",
     "//url/mojo:url_mojom_gurl_blink_cpp_sources",
   ]
   output_name = "blink_platform"
 
   sources = [
     "AsyncFileSystemCallbacks.h",
     "CalculationValue.h",
-    "CheckedInt.h",
     "ContentDecryptionModuleResult.h",
     "ContentSettingCallbacks.cpp",
     "ContentSettingCallbacks.h",
     "ContentType.cpp",
     "ContentType.h",
     "ContextMenu.cpp",
     "ContextMenu.h",
     "ContextMenuItem.cpp",
     "ContextMenuItem.h",
     "CrossThreadCopier.cpp",
@@ skipping 1735 matching lines @@
     "//third_party/WebKit/Source:inside_blink",
   ]
 
   deps = [
     ":test_support",
     "//cc/surfaces:surface_id",
     "//testing/gmock",
     "//testing/gtest",
   ]
 }