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 54bc62056f6f111507f346d9e662ed2f23c80da0..f25214fce82151898eeaba47a99b7a20abf2c936 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",
@@ -335,6 +334,10 @@ source_set("browser_sources") {
     "//content/browser",
   ]
 
+  if (is_posix) {
+    sources += [ "posix_file_descriptor_info.h" ]
+  }
+
   if (is_android) {
     deps += [ "//ui/android" ]
   }