Remove unused files linux.cc/.h and linuxfdwalk.c/.h.

webrtc/base/BUILD.gn

Index: webrtc/base/BUILD.gn
diff --git a/webrtc/base/BUILD.gn b/webrtc/base/BUILD.gn
index a6b177999fbaa84177bf9ac866a16be2b153a43d..e94bfeda49d76721c3cc94a6fff6a90e0fbebba5 100644
--- a/webrtc/base/BUILD.gn
+++ b/webrtc/base/BUILD.gn
@@ -557,13 +557,6 @@ rtc_static_library("rtc_base") {
       "window.h",
     ]
 
-    if (is_linux) {
-      sources += [
-        "linuxfdwalk.c",
-        "linuxfdwalk.h",
-      ]
-    }
-
     if (is_posix) {
       sources += [
         "latebindingsymboltable.cc",
@@ -697,13 +690,6 @@ rtc_static_library("rtc_base") {
     }
   }
 
-  if (is_linux || is_android) {
-    sources += [
-      "linux.cc",
-      "linux.h",
-    ]
-  }
-
   if (is_nacl) {
     deps += [ "//native_client_sdk/src/libraries/nacl_io" ]
     defines += [ "timezone=_timezone" ]