[protobuf] Fix potential double definition build errors.

third_party/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.
 
 config("protobuf_config") {
   include_dirs = [ "src" ]
   defines = [
     "GOOGLE_PROTOBUF_NO_RTTI",
     "GOOGLE_PROTOBUF_NO_STATIC_INITIALIZER",
   ]
@@ skipping 55 matching lines @@
   "src/google/protobuf/stubs/atomicops_internals_arm_qnx.h",
   "src/google/protobuf/stubs/atomicops_internals_atomicword_compat.h",
   "src/google/protobuf/stubs/atomicops_internals_generic_gcc.h",
   "src/google/protobuf/stubs/atomicops_internals_macosx.h",
   "src/google/protobuf/stubs/atomicops_internals_mips_gcc.h",
   "src/google/protobuf/stubs/atomicops_internals_pnacl.h",
   "src/google/protobuf/stubs/atomicops_internals_power.h",
   "src/google/protobuf/stubs/atomicops_internals_ppc_gcc.h",
   "src/google/protobuf/stubs/atomicops_internals_solaris.h",
   "src/google/protobuf/stubs/atomicops_internals_tsan.h",
-  "src/google/protobuf/stubs/atomicops_internals_x86_gcc.cc",
   "src/google/protobuf/stubs/atomicops_internals_x86_gcc.h",
   "src/google/protobuf/stubs/atomicops_internals_x86_msvc.cc",
   "src/google/protobuf/stubs/atomicops_internals_x86_msvc.h",
   "src/google/protobuf/stubs/atomic_sequence_num.h",
   "src/google/protobuf/stubs/bytestream.cc",
   "src/google/protobuf/stubs/bytestream.h",
   "src/google/protobuf/stubs/callback.h",
   "src/google/protobuf/stubs/casts.h",
   "src/google/protobuf/stubs/common.cc",
   "src/google/protobuf/stubs/common.h",
@@ skipping 105 matching lines @@
 
   deps = [
     "//build/config/sanitizers:deps",
   ]
 
   cflags = protobuf_lite_cflags
 
   if (is_component_build && is_linux && !is_chromeos) {
     deps += [ ":protobuf_globals" ]
   } else {
-    sources += [ "src/google/protobuf/globals.cc" ]
+    sources += [
+      "src/google/protobuf/globals.cc",

[Tom (Use chromium acct), 2017/03/21 18:06:21]

it would probably be better to define protobuf_globals_sources that contains
these 2 files, and add it here and in protobuf_full

[Peter Kasting, 2017/03/21 22:39:12]

Yes.  This way we won't list these in multiple different places which are easy
to not have in sync (as in the case of this bug).

[Eric Seckler, 2017/03/22 11:36:16]

Done.

+      "src/google/protobuf/stubs/atomicops_internals_x86_gcc.cc",
+    ]
   }
 
   # Required for component builds. See http://crbug.com/172800.
   if (is_component_build && (!is_linux || is_chromeos)) {
     public_configs += [ ":protobuf_use_dlls" ]
     defines = [ "LIBPROTOBUF_EXPORTS" ]
   }
 }
 
 # This is the full, heavy protobuf lib that's needed for c++ .protos that don't
 # specify the LITE_RUNTIME option. The protocol compiler itself (protoc) falls
 # into that category. Do not use in Chrome code.
 static_library("protobuf_full") {
   # Prevent people from depending on this outside our file.
   visibility = [
     ":*",
 
     # requires descriptors & reflection; testonly.
     "//third_party/libprotobuf-mutator:*",
   ]
 
   sources = protobuf_lite_sources
   sources += [

[Tom (Use chromium acct), 2017/03/21 18:06:21]

while we're here, can you change this to be:
sources = protobuf_lite_sources + protobuf_globals_sources + [ ...

[Eric Seckler, 2017/03/22 11:36:16]

Done.

     "src/google/protobuf/any.cc",
     "src/google/protobuf/any.h",
     "src/google/protobuf/any.pb.cc",
     "src/google/protobuf/any.pb.h",
     "src/google/protobuf/api.pb.cc",
     "src/google/protobuf/api.pb.h",
     "src/google/protobuf/compiler/importer.cc",
     "src/google/protobuf/compiler/importer.h",
     "src/google/protobuf/compiler/parser.cc",
     "src/google/protobuf/compiler/parser.h",
@@ skipping 42 matching lines @@
     "src/google/protobuf/reflection.h",
     "src/google/protobuf/reflection_internal.h",
     "src/google/protobuf/reflection_ops.cc",
     "src/google/protobuf/reflection_ops.h",
     "src/google/protobuf/service.cc",
     "src/google/protobuf/service.h",
     "src/google/protobuf/source_context.pb.cc",
     "src/google/protobuf/source_context.pb.h",
     "src/google/protobuf/struct.pb.cc",
     "src/google/protobuf/struct.pb.h",
+    "src/google/protobuf/stubs/atomicops_internals_x86_gcc.cc",
     "src/google/protobuf/stubs/mathlimits.cc",
     "src/google/protobuf/stubs/mathlimits.h",
     "src/google/protobuf/stubs/mathutil.h",
     "src/google/protobuf/stubs/singleton.h",
     "src/google/protobuf/stubs/substitute.cc",
     "src/google/protobuf/stubs/substitute.h",
     "src/google/protobuf/text_format.cc",
     "src/google/protobuf/text_format.h",
     "src/google/protobuf/timestamp.pb.cc",
     "src/google/protobuf/timestamp.pb.h",
@@ skipping 388 matching lines @@
     ":copy_google_protobuf_internal",
     ":copy_six",
   ]
 
   # Targets that depend on this should depend on the copied data files.
   data = get_target_outputs(":copy_google")
   data += get_target_outputs(":copy_six")
   data += get_target_outputs(":copy_google_protobuf")
   data += get_target_outputs(":copy_google_protobuf_internal")
 }