Fix GN linking issues.

content/browser/devtools/BUILD.gn

Index: content/browser/devtools/BUILD.gn
diff --git a/content/browser/devtools/BUILD.gn b/content/browser/devtools/BUILD.gn
index ffeb2491809cf04f3b7026b02cdfb6042a87968c..c5d2ab2b4e51bb3145deefcb846555b710acf40a 100644
--- a/content/browser/devtools/BUILD.gn
+++ b/content/browser/devtools/BUILD.gn
@@ -50,8 +50,8 @@ action("devtools_resources") {
   ]
 }
 
-action("devtools_protocol_constants") {
-  visibility = ":resources"
+action("gen_devtools_protocol_constants") {
+  visibility = ":devtools_protocol_constants"
 
   script = "//content/public/browser/devtools_protocol_constants_generator.py"
 
@@ -69,3 +69,8 @@ action("devtools_protocol_constants") {
     rebase_path(browser_protocol, root_build_dir),
   ]
 }
+
+source_set("devtools_protocol_constants") {
+  visibility = ":resources"
+  sources = get_target_outputs(":gen_devtools_protocol_constants")
+}