asset: add missing copyright header, fix typo.

Change-Id: I86feab77d053d384af74219df371b31a7f5d82f0
Reviewed-on: https://go-review.googlesource.com/11823
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>

asset/asset.go

@@ -1,3 +1,7 @@
+// Copyright 2015 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.
+
 // Package asset provides access to application-bundled assets.
 //
 // On Android, assets are accessed via android.content.res.AssetManager.
@@ -9,7 +13,7 @@
 // Resources can be loaded using the same relative paths.
 //
 // For consistency when debugging on a desktop, assets are read from a
-// directoy named assets under the current working directory.
+// directory named assets under the current working directory.
 package asset
 
 import "io"

asset/asset_darwin_armx.go

@@ -21,5 +21,4 @@ func openAsset(name string) (File, error) {
 		return nil, err
 	}
 	return f, nil
-
 }