diff --git a/error_code.h b/error_code.h
new file mode 100644
index 0000000..db023f7
--- /dev/null
+++ b/error_code.h
@@ -0,0 +1,107 @@
+// Copyright (c) 2013 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_ERROR_CODE_H__
+#define CHROMEOS_PLATFORM_UPDATE_ENGINE_ERROR_CODE_H__
+
+namespace chromeos_update_engine {
+
+// Action exit codes.
+enum ErrorCode {
+  kErrorCodeSuccess = 0,
+  kErrorCodeError = 1,
+  kErrorCodeOmahaRequestError = 2,
+  kErrorCodeOmahaResponseHandlerError = 3,
+  kErrorCodeFilesystemCopierError = 4,
+  kErrorCodePostinstallRunnerError = 5,
+  kErrorCodeSetBootableFlagError = 6,  // TODO(petkov): Unused. Recycle?
+  kErrorCodeInstallDeviceOpenError = 7,
+  kErrorCodeKernelDeviceOpenError = 8,
+  kErrorCodeDownloadTransferError = 9,
+  kErrorCodePayloadHashMismatchError = 10,
+  kErrorCodePayloadSizeMismatchError = 11,
+  kErrorCodeDownloadPayloadVerificationError = 12,
+  kErrorCodeDownloadNewPartitionInfoError = 13,
+  kErrorCodeDownloadWriteError = 14,
+  kErrorCodeNewRootfsVerificationError = 15,
+  kErrorCodeNewKernelVerificationError = 16,
+  kErrorCodeSignedDeltaPayloadExpectedError = 17,
+  kErrorCodeDownloadPayloadPubKeyVerificationError = 18,
+  kErrorCodePostinstallBootedFromFirmwareB = 19,
+  kErrorCodeDownloadStateInitializationError = 20,
+  kErrorCodeDownloadInvalidMetadataMagicString = 21,
+  kErrorCodeDownloadSignatureMissingInManifest = 22,
+  kErrorCodeDownloadManifestParseError = 23,
+  kErrorCodeDownloadMetadataSignatureError = 24,
+  kErrorCodeDownloadMetadataSignatureVerificationError = 25,
+  kErrorCodeDownloadMetadataSignatureMismatch = 26,
+  kErrorCodeDownloadOperationHashVerificationError = 27,
+  kErrorCodeDownloadOperationExecutionError = 28,
+  kErrorCodeDownloadOperationHashMismatch = 29,
+  kErrorCodeOmahaRequestEmptyResponseError = 30,
+  kErrorCodeOmahaRequestXMLParseError = 31,
+  kErrorCodeDownloadInvalidMetadataSize = 32,
+  kErrorCodeDownloadInvalidMetadataSignature = 33,
+  kErrorCodeOmahaResponseInvalid = 34,
+  kErrorCodeOmahaUpdateIgnoredPerPolicy = 35,
+  kErrorCodeOmahaUpdateDeferredPerPolicy = 36,
+  kErrorCodeOmahaErrorInHTTPResponse = 37,
+  kErrorCodeDownloadOperationHashMissingError = 38,
+  kErrorCodeDownloadMetadataSignatureMissingError = 39,
+  kErrorCodeOmahaUpdateDeferredForBackoff = 40,
+  kErrorCodePostinstallPowerwashError = 41,
+  kErrorCodeUpdateCanceledByChannelChange = 42,
+
+  // Note: When adding new error codes, please remember to add the
+  // error into one of the buckets in PayloadState::UpdateFailed method so
+  // that the retries across URLs and the payload backoff mechanism work
+  // correctly for those new error codes.
+
+  // Any code above this is sent to both Omaha and UMA as-is, except
+  // kErrorCodeOmahaErrorInHTTPResponse (see error code 2000 for more details).
+  // Codes/flags below this line is sent only to Omaha and not to UMA.
+
+  // kErrorCodeUmaReportedMax is not an error code per se, it's just the count
+  // of the number of enums above.  Add any new errors above this line if you
+  // want them to show up on UMA. Stuff below this line will not be sent to UMA
+  // but is used for other errors that are sent to Omaha. We don't assign any
+  // particular value for this enum so that it's just one more than the last
+  // one above and thus always represents the correct count of UMA metrics
+  // buckets, even when new enums are added above this line in future. See
+  // utils::SendErrorCodeToUma on how this enum is used.
+  kErrorCodeUmaReportedMax,
+
+  // use the 2xxx range to encode HTTP errors. These errors are available in
+  // Dremel with the individual granularity. But for UMA purposes, all these
+  // errors are aggregated into one: kErrorCodeOmahaErrorInHTTPResponse.
+  kErrorCodeOmahaRequestHTTPResponseBase = 2000,  // + HTTP response code
+
+  // TODO(jaysri): Move out all the bit masks into separate constants
+  // outside the enum as part of fixing bug 34369.
+  // Bit flags. Remember to update the mask below for new bits.
+
+  // Set if boot mode not normal.
+  kErrorCodeDevModeFlag        = 1 << 31,
+
+  // Set if resuming an interruped update.
+  kErrorCodeResumedFlag         = 1 << 30,
+
+  // Set if using a dev/test image as opposed to an MP-signed image.
+  kErrorCodeTestImageFlag       = 1 << 29,
+
+  // Set if using devserver or Omaha sandbox (using crosh autest).
+  kErrorCodeTestOmahaUrlFlag    = 1 << 28,
+
+  // Mask that indicates bit positions that are used to indicate special flags
+  // that are embedded in the error code to provide additional context about
+  // the system in which the error was encountered.
+  kErrorCodeSpecialFlags = (kErrorCodeDevModeFlag |
+                            kErrorCodeResumedFlag |
+                            kErrorCodeTestImageFlag |
+                            kErrorCodeTestOmahaUrlFlag)
+};
+
+}  // namespace chromeos_update_engine
+
+#endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_ACTION_PROCESSOR_H__