Improve process launch handle sharing API.

content/public/browser/BUILD.gn

Index: content/public/browser/BUILD.gn
diff --git a/content/public/browser/BUILD.gn b/content/public/browser/BUILD.gn
index 473549a648284e326abc93fa7fdf374dff2460a0..8a2bc1da6f29e995a02ed662bdbacda033bf4fe6 100644
--- a/content/public/browser/BUILD.gn
+++ b/content/public/browser/BUILD.gn
@@ -113,7 +113,6 @@ source_set("browser_sources") {
     "download_url_parameters.h",
     "favicon_status.cc",
     "favicon_status.h",
-    "file_descriptor_info.h",
     "focused_node_details.h",
     "font_list_async.h",
     "global_request_id.h",
@@ -334,6 +333,10 @@ source_set("browser_sources") {
     "//content/browser",
   ]
 
+  if (is_posix) {
+    sources += [ "posix_file_descriptor_info.h" ]
+  }
+
   if (is_android) {
     deps += [ "//ui/android" ]
   }