Correctly name header macros for src/snapshot/*.h.

src/snapshot/snapshot-source-sink.h

Index: src/snapshot/snapshot-source-sink.h
diff --git a/src/snapshot/snapshot-source-sink.h b/src/snapshot/snapshot-source-sink.h
index 6612029a9075bbbc40b794050f7cdf8c72152b36..c6c8df71b8cc735f6f382c5b97ea442592451a56 100644
--- a/src/snapshot/snapshot-source-sink.h
+++ b/src/snapshot/snapshot-source-sink.h
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef V8_SNAPSHOT_SOURCE_SINK_H_
-#define V8_SNAPSHOT_SOURCE_SINK_H_
+#ifndef V8_SNAPSHOT_SNAPSHOT_SOURCE_SINK_H_
+#define V8_SNAPSHOT_SNAPSHOT_SOURCE_SINK_H_
 
 #include "src/base/logging.h"
 #include "src/utils.h"
@@ -104,4 +104,4 @@ class SnapshotByteSink {
 }  // namespace v8::internal
 }  // namespace v8
 
-#endif  // V8_SNAPSHOT_SOURCE_SINK_H_
+#endif  // V8_SNAPSHOT_SNAPSHOT_SOURCE_SINK_H_