[protobuf] Fix potential double definition build errors.

third_party/protobuf/BUILD.gn

Index: third_party/protobuf/BUILD.gn
diff --git a/third_party/protobuf/BUILD.gn b/third_party/protobuf/BUILD.gn
index 6fb6d6ad30439ccee3fb4dcac22cec4b90c454f0..fbc3c3235415f2234a2c8464d38b84babb19a27b 100644
--- a/third_party/protobuf/BUILD.gn
+++ b/third_party/protobuf/BUILD.gn
@@ -73,7 +73,6 @@ protobuf_lite_sources = [
   "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",
@@ -199,7 +198,10 @@ target(link_target_type, "protobuf_lite") {
   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.
@@ -285,6 +287,7 @@ static_library("protobuf_full") {
     "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",