Move remoting::GetUsername() from remoting/base to remoting/host

remoting/base/util.h

Index: remoting/base/util.h
diff --git a/remoting/base/util.h b/remoting/base/util.h
index 5478c7fe29f14f5799d795c6fe33b679830ff359..c8c70210f686051ee474ffe0fbfe6931a2da6ebe 100644
--- a/remoting/base/util.h
+++ b/remoting/base/util.h
@@ -93,10 +93,6 @@ std::string ReplaceCrLfByLf(const std::string& in);
 // Checks if the given string is a valid UTF-8 string.
 bool StringIsUtf8(const char* data, size_t length);
 
-// Returns the username associated with this process, or the empty string on
-// error or if not implemented.
-std::string GetUsername();
-
 bool DoesRectContain(const webrtc::DesktopRect& a,
                      const webrtc::DesktopRect& b);