diff --git a/constants.h b/constants.h
index 4f335c3..b2c1de2 100644
--- a/constants.h
+++ b/constants.h
@@ -18,6 +18,7 @@
 extern const char kPrefsBackoffExpiryTime[];
 extern const char kPrefsCertificateReportToSendDownload[];
 extern const char kPrefsCertificateReportToSendUpdate[];
+extern const char kPrefsCurrentBytesDownloaded[];
 extern const char kPrefsCurrentResponseSignature[];
 extern const char kPrefsCurrentUrlFailureCount[];
 extern const char kPrefsCurrentUrlIndex[];
@@ -28,6 +29,7 @@
 extern const char kPrefsPayloadAttemptNumber[];
 extern const char kPrefsPreviousVersion[];
 extern const char kPrefsResumedUpdateFailures[];
+extern const char kPrefsTotalBytesDownloaded[];
 extern const char kPrefsUpdateCheckCount[];
 extern const char kPrefsUpdateCheckResponseHash[];
 extern const char kPrefsUpdateFirstSeenAt[];
@@ -41,6 +43,23 @@
 extern const char kPrefsUpdateTimestampStart[];
 extern const char kPrefsUpdateDurationUptime[];
 
+// A download source is any combination of protocol and server (that's of
+// interest to us when looking at UMA metrics) using which we may download
+// the payload.
+typedef enum {
+  kDownloadSourceHttpsServer, // UMA Binary representation: 0001
+  kDownloadSourceHttpServer,  // UMA Binary representation: 0010
+
+  // Note: Add new sources only above this line.
+  kNumDownloadSources
+} DownloadSource;
+
+// The default number of UMA buckets for metrics.
+const int kNumDefaultUmaBuckets = 50;
+
+// General constants
+const int kNumBytesInOneMiB = 1024 * 1024;
+
 }  // namespace chromeos_update_engine
 
 #endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_CONSTANTS_H