Fix linker warning in broadcast_channel.mojom-blink.obj.

third_party/WebKit/Source/platform/BUILD.gn

Index: third_party/WebKit/Source/platform/BUILD.gn
diff --git a/third_party/WebKit/Source/platform/BUILD.gn b/third_party/WebKit/Source/platform/BUILD.gn
index 92e9fcdd63f903de65c52004f478cb70015fd41c..27df20ebdfc3a0c3748dc46f7007d96cebd352dc 100644
--- a/third_party/WebKit/Source/platform/BUILD.gn
+++ b/third_party/WebKit/Source/platform/BUILD.gn
@@ -103,7 +103,13 @@ action("http_names") {
 
 # RuntimeEnabledFeatures action in make_platform_generated in
 # platform_generated.gyp
-action("runtime_enabled_features") {
+action("runtime_enabled_features_action") {
+  visibility = []  # Allow re-assignment of list.
+  visibility = [
+    ":*",
+    "//third_party/WebKit/Source/platform/weborigin",
+  ]
+
   script = "../build/scripts/make_runtime_features.py"
 
   runtime_enabled_features_in = "RuntimeEnabledFeatures.in"
@@ -305,7 +311,32 @@ group("make_platform_generated") {
     ":inspector_debugger_script",
     ":inspector_injected_script",
     ":inspector_protocol_sources",
-    ":runtime_enabled_features",
+    ":runtime_enabled_features_action",
+  ]
+}
+
+component("runtime_enabled_features") {
+  visibility = []  # Allow re-assignment of list.
+  visibility = [
+    ":*",
+    "//third_party/WebKit/Source/platform/weborigin",
+  ]
+
+  sources = get_target_outputs(":runtime_enabled_features_action")
+
+  defines = [
+    "RUNTIME_ENABLED_FEATURES_IMPLEMENTATION=1",
+    "INSIDE_BLINK",
+  ]
+
+  configs += [
+    "//third_party/WebKit/Source:config",
+    "//third_party/WebKit/Source:non_test_config",
+  ]
+
+  public_deps = [
+    ":runtime_enabled_features_action",
+    "//third_party/WebKit/Source/wtf",
   ]
 }
 
@@ -331,8 +362,7 @@ component("platform") {
              get_target_outputs(":http_names") +
              get_target_outputs(":inspector_debugger_script") +
              get_target_outputs(":inspector_injected_script") +
-             get_target_outputs(":inspector_protocol_sources") +
-             get_target_outputs(":runtime_enabled_features")
+             get_target_outputs(":inspector_protocol_sources")
 
   configs += [
     # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
@@ -353,6 +383,7 @@ component("platform") {
 
   public_deps = [
     ":make_platform_generated",
+    ":runtime_enabled_features",
     "//base",
     "//cc",
     "//gpu/command_buffer/client:gles2_c_lib",
@@ -361,6 +392,7 @@ component("platform") {
     "//net",
     "//skia",
     "//third_party:jpeg",
+    "//third_party/WebKit/Source/platform/weborigin",
     "//third_party/WebKit/Source/wtf",
     "//third_party/iccjpeg",
     "//third_party/libpng",