Enable Wextra and Wno-unused-parameters in default cflags

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")
 if (current_cpu == "arm") {
   import("//build/config/arm.gni")
 }
 if (current_cpu == "mipsel" || current_cpu == "mips64el") {
@@ skipping 805 matching lines @@
     "-Wno-char-subscripts",
 
     # Warns on switches on enums that cover all enum values but
     # also contain a default: branch. Chrome is full of that.
     "-Wno-covered-switch-default",
 
     # Clang considers the `register` keyword as deprecated, but e.g.
     # code generated by flex (used in angle) contains that keyword.
     # http://crbug.com/255186
     "-Wno-deprecated-register",
+
+    "-Wno-unused-parameter",
   ]
 
   # NaCl's Clang compiler and Chrome's hermetic Clang compiler will almost
   # always have different versions. Certain flags may not be recognized by
   # one version or the other.
   if (!is_nacl) {
     # Flags NaCl (Clang 3.7) does not recognize.
     default_warning_flags += [
       # TODO(smklein): Enable this, crbug.com/507717
       "-Wno-shift-negative-value",
     ]
   }
 }
 
 # chromium_code ---------------------------------------------------------------
 #
 # Toggles between higher and lower warnings for code that is (or isn't)
 # part of Chromium.
 
 config("chromium_code") {
   cflags = [
     "-Wall",
-
-    # GCC turns on -Wsign-compare for C++ under -Wall, but clang doesn't,
-    # so we specify it explicitly.
-    # TODO(fischman): remove this if http://llvm.org/PR10448 obsoletes it.
-    # http://code.google.com/p/chromium/issues/detail?id=90453
-    "-Wsign-compare",
+    "-Wextra",
   ]
 
   # In Chromium code, we define __STDC_foo_MACROS in order to get the
   # C99 macros on Mac and Linux.
   defines = [
     "__STDC_CONSTANT_MACROS",
     "__STDC_FORMAT_MACROS",
   ]
 
   if (!is_debug && !using_sanitizer &&
@@ skipping 253 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)
   }
 }