Fix GN missing headers in //base

base/third_party/libevent/BUILD.gn

Index: base/third_party/libevent/BUILD.gn
diff --git a/base/third_party/libevent/BUILD.gn b/base/third_party/libevent/BUILD.gn
index 5dd0f7070e89d94c6020ae494707bfc6418967b6..e934454a10f9696121ec472de0d347e9e307ee5a 100644
--- a/base/third_party/libevent/BUILD.gn
+++ b/base/third_party/libevent/BUILD.gn
@@ -9,28 +9,53 @@ static_library("libevent") {
     "buffer.c",
     "evbuffer.c",
     "evdns.c",
+    "evdns.h",
+    "event-config.h",
+    "event-internal.h",
     "event.c",
+    "event.h",
     "event_tagging.c",
+    "evhttp.h",
+    "evrpc-internal.h",
     "evrpc.c",
+    "evrpc.h",
+    "evsignal.h",
     "evutil.c",
+    "evutil.h",
+    "http-internal.h",
     "http.c",
     "log.c",
+    "log.h",
+    "min_heap.h",
     "poll.c",
     "select.c",
     "signal.c",
+    "strlcpy-internal.h",
     "strlcpy.c",
   ]
 
   defines = [ "HAVE_CONFIG_H" ]
 
   if (is_mac || is_ios) {
-    sources += [ "kqueue.c" ]
+    sources += [
+      "kqueue.c",
+      "mac/config.h",
+      "mac/event-config.h",
+    ]
     include_dirs = [ "mac" ]
   } else if (is_linux) {
-    sources += [ "epoll.c" ]
+    sources += [
+      "epoll.c",
+      "linux/config.h",
+      "linux/event-config.h",
+    ]
     include_dirs = [ "linux" ]
   } else if (is_android) {
-    sources += [ "epoll.c" ]
+    sources += [
+      "android/config.h",
+      "android/event-config.h",
+      "epoll.c",
+    ]
     include_dirs = [ "android" ]
   } else if (is_nacl_nonsfi) {
     sources -= [