clang/win: Let some chromium_code targets build with -Wextra.

build/config/compiler/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/android/config.gni")
 import("//build/config/chrome_build.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/nacl/config.gni")
 import("//build/toolchain/ccache.gni")
 
@@ skipping 765 matching lines @@
         "-Wno-microsoft-enum-value",  # http://crbug.com/505296
         "-Wno-unknown-pragmas",  # http://crbug.com/505314
         "-Wno-microsoft-cast",  # http://crbug.com/550065
 
         # Disable unused-value (crbug.com/505318) except -Wunused-result.
         "-Wno-unused-value",
         "-Wunused-result",
       ]
     }
   } else {
-    # Common GCC warning setup.
-    cflags += [
-      # Enables.
-      "-Wendif-labels",  # Weird old-style text after an #endif.
-
-      # Disables.
-      "-Wno-missing-field-initializers",  # "struct foo f = {0};"
-      "-Wno-unused-parameter",  # Unused function parameters.
-    ]
-
     if (treat_warnings_as_errors) {
       cflags += [ "-Werror" ]
     }
 
     if (is_mac) {
       cflags += [ "-Wnewline-eof" ]
       if (!is_nacl) {
         # When compiling Objective-C, warns if a method is used whose
         # availability is newer than the deployment target. This is not
         # required when compiling Chrome for iOS.
@@ skipping 21 matching lines @@
     }
 
     if (gcc_version >= 48) {
       # Don't warn about the "typedef 'foo' locally defined but not used"
       # for gcc 4.8.
       # TODO: remove this flag once all builds work. See crbug.com/227506
       cflags += [ "-Wno-unused-local-typedefs" ]
     }
   }
 
+  # Common Clang and GCC warning setup.
+  if (!is_win || is_clang) {
+    cflags += [
+      # Enables.
+      "-Wendif-labels",  # Weird old-style text after an #endif.
+
+      # Disables.
+      "-Wno-missing-field-initializers",  # "struct foo f = {0};"
+      "-Wno-unused-parameter",  # Unused function parameters.
+    ]
+  }
+
   if (is_clang) {
     cflags += [
       # This warns on using ints as initializers for floats in
       # initializer lists (e.g. |int a = f(); CGSize s = { a, a };|),
       # which happens in several places in chrome code. Not sure if
       # this is worth fixing.
       "-Wno-c++11-narrowing",
 
       # Warns on switches on enums that cover all enum values but
       # also contain a default: branch. Chrome is full of that.
@@ skipping 466 matching lines @@
   if (symbol_level == 0) {
     configs = [ ":no_symbols" ]
   } else if (symbol_level == 1) {
     configs = [ ":minimal_symbols" ]
   } else if (symbol_level == 2) {
     configs = [ ":symbols" ]
   } else {
     assert(false)
   }
 }