Prepare for -Wall for third-party code, -Wextra for chromium_code

third_party/android_protobuf/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.
 
 if (current_toolchain == host_toolchain) {
+  config("android_protoc_warnings") {
+    cflags = [
+      "-Wno-null-conversion",
+      "-Wno-tautological-undefined-compare",
+      "-Wno-unused-function",
+      "-Wno-unused-local-typedef",
+    ]
+  }
+
   # GYP: //third_party/android_protobuf/android_protobuf.gyp:android_protoc
   executable("android_protoc") {
     configs -= [ "//build/config/compiler:chromium_code" ]
-    configs += [ "//build/config/compiler:no_chromium_code" ]
+    configs += [
+      "//build/config/compiler:no_chromium_code",
+
+      # Must be after no_chromium_code so warning flags are ordered correctly.
+      ":android_protoc_warnings",
+    ]
 
     deps = [
       "//build/config/sanitizers:deps",
       "//third_party/zlib",
     ]
 
     sources = [
       "src/src/google/protobuf/compiler/code_generator.cc",
       "src/src/google/protobuf/compiler/command_line_interface.cc",
       "src/src/google/protobuf/compiler/cpp/cpp_enum.cc",
@@ skipping 87 matching lines @@
       "src/src/google/protobuf/unknown_field_set.cc",
       "src/src/google/protobuf/wire_format.cc",
       "src/src/google/protobuf/wire_format_lite.cc",
     ]
 
     include_dirs = [
       "src/android",
       "src/src",
     ]
 
-    if (is_clang) {
-      cflags = [
-        "-Wno-null-conversion",
-        "-Wno-tautological-undefined-compare",
-      ]
-    }
     defines = [
       # This macro must be defined to suppress the use
       # of dynamic_cast<>, which requires RTTI.
       "GOOGLE_PROTOBUF_NO_RTTI",
       "GOOGLE_PROTOBUF_NO_STATIC_INITIALIZER",
     ]
   }
 }
 
 if (is_android) {
@@ skipping 10 matching lines @@
       "src/java/src/main/java/com/google/protobuf/nano/FieldData.java",
       "src/java/src/main/java/com/google/protobuf/nano/InternalNano.java",
       "src/java/src/main/java/com/google/protobuf/nano/InvalidProtocolBufferNanoException.java",
       "src/java/src/main/java/com/google/protobuf/nano/MessageNano.java",
       "src/java/src/main/java/com/google/protobuf/nano/MessageNanoPrinter.java",
       "src/java/src/main/java/com/google/protobuf/nano/UnknownFieldData.java",
       "src/java/src/main/java/com/google/protobuf/nano/WireFormatNano.java",
     ]
   }
 }