Remove third_party/golang.org/x/mobile as it is no longer used with Go 1.5.

third_party/go/src/golang.org/x/mobile/font/font.go

Index: third_party/go/src/golang.org/x/mobile/font/font.go
diff --git a/third_party/go/src/golang.org/x/mobile/font/font.go b/third_party/go/src/golang.org/x/mobile/font/font.go
deleted file mode 100644
index 38f6ba6761b3ebaca434090a4c150078872a827d..0000000000000000000000000000000000000000
--- a/third_party/go/src/golang.org/x/mobile/font/font.go
+++ /dev/null
@@ -1,27 +0,0 @@
-// Copyright 2014 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// +build linux darwin
-
-package font
-
-// Default returns the default system font.
-// The font is encoded as a TTF.
-func Default() []byte {
-	b, err := buildDefault()
-	if err != nil {
-		panic(err)
-	}
-	return b
-}
-
-// Monospace returns the default system fixed-pitch font.
-// The font is encoded as a TTF.
-func Monospace() []byte {
-	b, err := buildMonospace()
-	if err != nil {
-		panic(err)
-	}
-	return b
-}