Move MetricsStateManager into the Metrics component.

components/metrics/metrics_pref_names.h

Index: components/metrics/metrics_pref_names.h
diff --git a/components/metrics/metrics_pref_names.h b/components/metrics/metrics_pref_names.h
index 4c799c7d5f26e7cb3bb3a7021dbaaeb95a3ea35b..2f59fef0559e469bd6f470e40f297f3f544d8984 100644
--- a/components/metrics/metrics_pref_names.h
+++ b/components/metrics/metrics_pref_names.h
@@ -9,11 +9,17 @@ namespace metrics {
 namespace prefs {
 
 // Alphabetical list of preference names specific to the metrics
-// component. Keep alphabetized, and document each in the .cc file.
+// component. Document each in the .cc file.
+extern const char kMetricsClientID[];
 extern const char kMetricsInitialLogs[];
+extern const char kMetricsLowEntropySource[];
 extern const char kMetricsMachineId[];
+extern const char kMetricsOldClientID[];
+extern const char kMetricsOldLowEntropySource[];
 extern const char kMetricsOngoingLogs[];
 extern const char kMetricsResetIds[];
+extern const char kMetricsReportingEnabledTimestamp[];
+extern const char kMetricsSessionID[];
 
 }  // namespace prefs
 }  // namespace metrics