Don't use $USER for Local Login check

remoting/base/util.cc

Index: remoting/base/util.cc
diff --git a/remoting/base/util.cc b/remoting/base/util.cc
index 58734229aa733d83c430291913bd389dc9564ddf..53b121352954d103a343ea887626e2abce36d110 100644
--- a/remoting/base/util.cc
+++ b/remoting/base/util.cc
@@ -13,6 +13,12 @@
 #include "media/base/yuv_convert.h"
 #include "third_party/skia/include/core/SkRegion.h"
 
+#if defined(OS_POSIX)
+#include <pwd.h>
+#include <sys/types.h>
+#include <unistd.h>
+#endif  // defined(OS_POSIX)
+
 using media::VideoFrame;
 
 namespace remoting {
@@ -311,4 +317,21 @@ bool StringIsUtf8(const char* data, size_t length) {
   return true;
 }
 
+std::string GetUsername() {
+#if defined(OS_POSIX)
+  long buf_size = sysconf(_SC_GETPW_R_SIZE_MAX);
+  if (buf_size <= 0)
+    return std::string();
+  scoped_array<char> buf(new char[buf_size]);
+  struct passwd passwd;
+  struct passwd* passwd_result = NULL;
+  getpwuid_r(getuid(), &passwd, buf.get(), buf_size, &passwd_result);
+  if (!passwd_result)
+    return std::string();
+  return std::string(passwd_result->pw_name);
+#else  // !defined(OS_POSIX)
+  return std::string();
+#endif  // defined(OS_POSIX)
+}
+
 }  // namespace remoting