Make MetricsService save compressed logs to local state.

components/metrics/compression_utils.h

Index: components/metrics/compression_utils.h
===================================================================
--- components/metrics/compression_utils.h	(working copy)
+++ components/metrics/compression_utils.h	(working copy)
@@ -2,16 +2,19 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef COMPONENTS_METRICS_NET_COMPRESSION_UTILS_H_
-#define COMPONENTS_METRICS_NET_COMPRESSION_UTILS_H_
+#ifndef COMPONENTS_METRICS_COMPRESSION_UTILS_H_
+#define COMPONENTS_METRICS_COMPRESSION_UTILS_H_
 
 #include <string>
 
 namespace metrics {
 
-// Compresses the text in |input| using gzip, storing the result in |output|.
+// Compresses the data in |input| using gzip, storing the result in |output|.
 bool GzipCompress(const std::string& input, std::string* output);
 
+// Uncompresses the data in |input| using gzip, storing the result in |output|.
+bool GzipUncompress(const std::string& input, std::string* output);
+
 }  // namespace metrics
 
-#endif  // COMPONENTS_METRICS_NET_COMPRESSION_UTILS_H_
+#endif  // COMPONENTS_METRICS_COMPRESSION_UTILS_H_