Move storage package under registry package

Signed-off-by: Stephen J Day <stephen.day@docker.com>

registry/storage/layerreader.go

@@ -0,0 +1,30 @@
+package storage
+
+import (
+	"time"
+
+	"github.com/docker/distribution/digest"
+)
+
+// layerReadSeeker implements Layer and provides facilities for reading and
+// seeking.
+type layerReader struct {
+	fileReader
+
+	name   string // repo name of this layer
+	digest digest.Digest
+}
+
+var _ Layer = &layerReader{}
+
+func (lrs *layerReader) Name() string {
+	return lrs.name
+}
+
+func (lrs *layerReader) Digest() digest.Digest {
+	return lrs.digest
+}
+
+func (lrs *layerReader) CreatedAt() time.Time {
+	return lrs.modtime
+}