Added "-Wno-signed-enum-bitfield" flag to not trigger Clang warning

skia/BUILD.gn

 # Copyright (c) 2013 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("//printing/features/features.gni")
 import("//testing/test.gni")
 import("//third_party/skia/gn/shared_sources.gni")
 
@@ skipping 463 matching lines @@
     sources += [
       "//third_party/skia/src/ports/SkFontHost_mac.cpp",
       "//third_party/skia/src/utils/mac/SkCreateCGImageRef.cpp",
       "//third_party/skia/src/utils/mac/SkStream_mac.cpp",
     ]
     set_sources_assignment_filter(sources_assignment_filter)
 
     # SkFontHost_mac.cpp uses API deprecated in iOS 7, crbug.com/408571
     cflags = [ "-Wno-deprecated-declarations" ]
   }
+
+  if (is_clang) {
+    # Skia won't build with the enum bitfield warning in Clang, crbug.com/648462
+    cflags += [ "-Wno-signed-enum-bitfield" ]
+  }
 }
 
 # Separated out so it can be compiled with different flags for SSE.
 if (!skia_build_no_opts) {
   if (current_cpu == "arm64") {
     source_set("skia_opts_crc32") {
       sources = skia_opts.crc32_sources
       cflags = [ "-march=armv8-a+crc" ]
       visibility = [ ":skia_opts" ]
       configs -= [ "//build/config/compiler:chromium_code" ]
@@ skipping 231 matching lines @@
 
     deps = [
       ":skia",
       "//base",
       "//base/test:test_support",
       "//build/config/sanitizers:deps",
       "//build/win:default_exe_manifest",
     ]
   }
 }