Use new GN features in the build.

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 7d42a00dd6a9c36da573ed5c9b31528ec60410aa..2c8d34688e5ae09a2a7d565e08dbb90bf9b22f25 100644
--- a/third_party/protobuf/BUILD.gn
+++ b/third_party/protobuf/BUILD.gn
@@ -19,7 +19,7 @@ config("protobuf_config") {
   ]
 }
 
-if (component_mode == "shared_library") {
+if (is_component_build) {
   config("protobuf_use_dlls") {
     defines = [ "PROTOBUF_USE_DLLS" ]
   }
@@ -103,7 +103,7 @@ component("protobuf_lite") {
   cflags = protobuf_lite_cflags
 
   # Required for component builds. See http://crbug.com/172800.
-  if (component_mode == "shared_library") {
+  if (is_component_build) {
     public_configs += [ ":protobuf_use_dlls" ]
     defines = [ "LIBPROTOBUF_EXPORTS" ]
   }