GN: Fix Windows Clang errors

webrtc/base/BUILD.gn

 # Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 import("//build/config/crypto.gni")
 import("//build/config/ui.gni")
@@ skipping 490 matching lines @@
         "diskcache_win32.cc",
         "diskcache_win32.h",
         "win32regkey.cc",
         "win32regkey.h",
         "win32socketinit.cc",
         "win32socketinit.h",
         "win32socketserver.cc",
         "win32socketserver.h",
       ]
     }
+    if (is_win && is_clang) {
+      cflags += [
+        # Disable warnings failing when compiling with Clang on Windows.
+        # https://bugs.chromium.org/p/webrtc/issues/detail?id=5366
+        "-Wno-sign-compare",
+        "-Wno-missing-braces",
+      ]
+    }
+
     if (rtc_build_json) {
       deps += [ "//third_party/jsoncpp" ]
     } else {
       include_dirs = [ "$rtc_jsoncpp_root" ]
 
       # When defined changes the include path for json.h to where it is
       # expected to be when building json outside of the standalone build.
       defines += [ "WEBRTC_EXTERNAL_JSON" ]
     }
   }  # !build_with_chromium
@@ skipping 188 matching lines @@
       "java/src/org/webrtc/Logging.java",
       "java/src/org/webrtc/Size.java",
       "java/src/org/webrtc/ThreadUtils.java",
     ]
 
     deps = [
       "//base:base_java",
     ]
   }
 }