diff --git a/metrics.h b/metrics.h
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+++ b/metrics.h
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+// Copyright 2014 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROMEOS_PLATFORM_UPDATE_ENGINE_METRICS_H_
+#define CHROMEOS_PLATFORM_UPDATE_ENGINE_METRICS_H_
+
+#include <base/time/time.h>
+
+#include "update_engine/constants.h"
+#include "update_engine/error_code.h"
+
+namespace chromeos_update_engine {
+
+class SystemState;
+
+namespace metrics {
+
+// UpdateEngine.Daily.* metrics.
+extern const char kMetricDailyOSAgeDays[];
+
+// UpdateEngine.Check.* metrics.
+extern const char kMetricCheckDownloadErrorCode[];
+extern const char kMetricCheckReaction[];
+extern const char kMetricCheckResult[];
+extern const char kMetricCheckTimeSinceLastCheckMinutes[];
+extern const char kMetricCheckTimeSinceLastCheckUptimeMinutes[];
+
+// UpdateEngine.Attempt.* metrics.
+extern const char kMetricAttemptNumber[];
+extern const char kMetricAttemptPayloadType[];
+extern const char kMetricAttemptPayloadSizeMiB[];
+extern const char kMetricAttemptDurationMinutes[];
+extern const char kMetricAttemptDurationUptimeMinutes[];
+extern const char kMetricAttemptTimeSinceLastAttemptSeconds[];
+extern const char kMetricAttemptTimeSinceLastAttemptUptimeSeconds[];
+extern const char kMetricAttemptPayloadBytesOffset[];
+extern const char kMetricAttemptPayloadBytesNeeded[];
+extern const char kMetricAttemptPayloadBytesDownloaded[];
+extern const char kMetricAttemptPayloadDownloadSpeedKBps[];
+extern const char kMetricAttemptDownloadSource[];
+extern const char kMetricAttemptResult[];
+extern const char kMetricAttemptInternalErrorCode[];
+extern const char kMetricAttemptDownloadErrorCode[];
+
+// UpdateEngine.SuccessfulUpdate.* metrics.
+extern const char kMetricSuccessfulUpdateAttemptCount[];
+extern const char kMetricSuccessfulUpdateBytesDownloadedMiB[];
+extern const char kMetricSuccessfulUpdateDownloadOverheadPercentage[];
+extern const char kMetricSuccessfulUpdateDownloadSourcesUsed[];
+extern const char kMetricSuccessfulUpdatePayloadType[];
+extern const char kMetricSuccessfulUpdatePayloadSizeMiB[];
+extern const char kMetricSuccessfulUpdateTotalDurationMinutes[];
+extern const char kMetricSuccessfulUpdateRebootCount[];
+extern const char kMetricSuccessfulUpdateUpdatesAbandonedCount[];
+extern const char kMetricSuccessfulUpdateUrlSwitchCount[];
+
+// UpdateEngine.* metrics.
+extern const char kMetricFailedUpdateCount[];
+extern const char kMetricInstallDateProvisioningSource[];
+extern const char kMetricTimeToRebootMinutes[];
+
+// The possible outcomes when checking for updates.
+//
+// This is used in the UpdateEngine.Check.Result histogram.
+enum class CheckResult {
+  kUpdateAvailable,    // Response indicates an update is available.
+  kNoUpdateAvailable,  // Response indicates no updates are available.
+  kDownloadError,      // Error downloading response from Omaha.
+  kParsingError,       // Error parsing response.
+  kRebootPending,      // No update check was performed a reboot is pending.
+
+  kNumConstants,
+  kUnset = -1
+};
+
+// Possible ways a device can react to a new update being available.
+//
+// This is used in the UpdateEngine.Check.Reaction histogram.
+enum class CheckReaction {
+  kUpdating,    // Device proceeds to download and apply update.
+  kIgnored  ,   // Device-policy dictates ignoring the update.
+  kDeferring,   // Device-policy dictates waiting.
+  kBackingOff,  // Previous errors dictates waiting.
+
+  kNumConstants,
+  kUnset = -1
+};
+
+// The possible ways that downloading from a HTTP or HTTPS server can fail.
+//
+// This is used in the UpdateEngine.Check.DownloadErrorCode and
+// UpdateEngine.Attempt.DownloadErrorCode histograms.
+enum class DownloadErrorCode {
+  // Errors that can happen in the field. See http://crbug.com/355745
+  // for how we plan to add more detail in the future.
+  kDownloadError = 0,  // Error downloading data from server.
+
+  // IMPORTANT: When adding a new error code, add at the bottom of the
+  // above block and before the kInputMalformed field. This
+  // is to ensure that error codes are not reordered.
+
+  // This error code is used to convey that malformed input was given
+  // to the utils::GetDownloadErrorCode() function. This should never
+  // happen but if it does it's because of an internal update_engine
+  // error and we're interested in knowing this.
+  kInputMalformed = 100,
+
+  // Bucket for capturing HTTP status codes not in the 200-599
+  // range. This should never happen in practice but if it does we
+  // want to know.
+  kHttpStatusOther = 101,
+
+  // Above 200 and below 600, the value is the HTTP status code.
+  kHttpStatus200 = 200,
+
+  kNumConstants = 600,
+
+  kUnset = -1
+};
+
+// Possible ways an update attempt can end.
+//
+// This is used in the UpdateEngine.Attempt.Result histogram.
+enum class AttemptResult {
+  kUpdateSucceeded,             // The update succeeded.
+  kInternalError,               // An internal error occurred.
+  kPayloadDownloadError,        // Failure while downloading payload.
+  kMetadataMalformed,           // Metadata was malformed.
+  kOperationMalformed,          // An operation was malformed.
+  kOperationExecutionError,     // An operation failed to execute.
+  kMetadataVerificationFailed,  // Metadata verification failed.
+  kPayloadVerificationFailed,   // Payload verification failed.
+  kVerificationFailed,          // Root or Kernel partition verification failed.
+  kPostInstallFailed,           // The postinstall step failed.
+  kAbnormalTermination,         // The attempt ended abnormally.
+
+  kNumConstants,
+
+  kUnset = -1
+};
+
+// Helper function to report metrics reported once a day. The
+// following metrics are reported:
+//
+//  |kMetricDailyOSAgeDays|
+void ReportDailyMetrics(SystemState *system_state,
+                        base::TimeDelta os_age);
+
+// Helper function to report metrics after completing an update check
+// with the ChromeOS update server ("Omaha"). The following metrics
+// are reported:
+//
+//  |kMetricCheckResult|
+//  |kMetricCheckReaction|
+//  |kMetricCheckDownloadErrorCode|
+//  |kMetricCheckTimeSinceLastCheckMinutes|
+//  |kMetricCheckTimeSinceLastCheckUptimeMinutes|
+//
+// The |kMetricCheckResult| metric will only be reported if |result|
+// is not |kUnset|.
+//
+// The |kMetricCheckReaction| metric will only be reported if
+// |reaction| is not |kUnset|.
+//
+// The |kMetricCheckDownloadErrorCode| will only be reported if
+// |download_error_code| is not |kUnset|.
+//
+// The values for the |kMetricCheckTimeSinceLastCheckMinutes| and
+// |kMetricCheckTimeSinceLastCheckUptimeMinutes| metrics are
+// automatically reported and calculated by maintaining persistent
+// and process-local state variables.
+void ReportUpdateCheckMetrics(SystemState *system_state,
+                              CheckResult result,
+                              CheckReaction reaction,
+                              DownloadErrorCode download_error_code);
+
+
+// Helper function to report metrics after the completion of each
+// update attempt. The following metrics are reported:
+//
+//  |kMetricAttemptNumber|
+//  |kMetricAttemptPayloadType|
+//  |kMetricAttemptPayloadSizeMiB|
+//  |kMetricAttemptDurationSeconds|
+//  |kMetricAttemptDurationUptimeSeconds|
+//  |kMetricAttemptTimeSinceLastAttemptMinutes|
+//  |kMetricAttemptTimeSinceLastAttemptUptimeMinutes|
+//  |kMetricAttemptPayloadBytesDownloadedMiB|
+//  |kMetricAttemptPayloadDownloadSpeedKBps|
+//  |kMetricAttemptDownloadSource|
+//  |kMetricAttemptResult|
+//  |kMetricAttemptInternalErrorCode|
+//  |kMetricAttemptDownloadErrorCode|
+//
+// The |kMetricAttemptInternalErrorCode| metric will only be reported
+// if |internal_error_code| is not |kErrorSuccess|.
+//
+// The |kMetricAttemptDownloadErrorCode| metric will only be
+// reported if |payload_download_error_code| is not |kUnset|.
+//
+// The values for the |kMetricAttemptTimeSinceLastAttemptMinutes| and
+// |kMetricAttemptTimeSinceLastAttemptUptimeMinutes| metrics are
+// automatically calculated and reported by maintaining persistent and
+// process-local state variables.
+void ReportUpdateAttemptMetrics(
+    SystemState *system_state,
+    int attempt_number,
+    PayloadType payload_type,
+    base::TimeDelta duration,
+    base::TimeDelta duration_uptime,
+    int64_t payload_size,
+    int64_t payload_bytes_downloaded,
+    int64_t payload_download_speed_bps,
+    DownloadSource download_source,
+    AttemptResult attempt_result,
+    ErrorCode internal_error_code,
+    DownloadErrorCode payload_download_error_code);
+
+// Helper function to report the after the completion of a successful
+// update attempt. The following metrics are reported:
+//
+//  |kMetricSuccessfulUpdateAttemptCount|
+//  |kMetricSuccessfulUpdateUpdatesAbandonedCount|
+//  |kMetricSuccessfulUpdatePayloadType|
+//  |kMetricSuccessfulUpdatePayloadSizeMiB|
+//  |kMetricSuccessfulUpdateBytesDownloadedMiBHttpsServer|
+//  |kMetricSuccessfulUpdateBytesDownloadedMiBHttpServer|
+//  |kMetricSuccessfulUpdateBytesDownloadedMiBHttpPeer|
+//  |kMetricSuccessfulUpdateBytesDownloadedMiB|
+//  |kMetricSuccessfulUpdateDownloadSourcesUsed|
+//  |kMetricSuccessfulUpdateDownloadOverheadPercentage|
+//  |kMetricSuccessfulUpdateTotalDurationMinutes|
+//  |kMetricSuccessfulUpdateRebootCount|
+//  |kMetricSuccessfulUpdateUrlSwitchCount|
+//
+// The values for the |kMetricSuccessfulUpdateDownloadSourcesUsed| are
+// |kMetricSuccessfulUpdateBytesDownloadedMiB| metrics automatically
+// calculated from examining the |num_bytes_downloaded| array.
+void ReportSuccessfulUpdateMetrics(
+    SystemState *system_state,
+    int attempt_count,
+    int updates_abandoned_count,
+    PayloadType payload_type,
+    int64_t payload_size,
+    int64_t num_bytes_downloaded[kNumDownloadSources],
+    int download_overhead_percentage,
+    base::TimeDelta total_duration,
+    int reboot_count,
+    int url_switch_count);
+
+}  // namespace metrics
+
+}  // namespace chromeos_update_engine
+
+#endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_METRICS_H_