Segregate UMA metrics for production scenarios from test scenarios.

Currently we separate the UMA metrics only by one category: whether the
device is in dev mode or not. In addition, we need to exclude the noise
from these two categories:
1. Most of our testing on MP-signed images which are performed
with autest.
2. All our hwlab tests run in non-dev mode but they use dev-signed images
with dev-firmware keys.

So this CL defines additional bit fields to represent these states and
if any of these three flags are set, the UMA metric is sent to a
DevModeErrorCodes bucket. Thus the NormalErrorCodes bucket will have only
the production errors and thus we can monitor more effectively.

BUG=chromium-os:37613
TEST=Updated unit tests, ran on ZGB for all scenarios.
Change-Id: Id9cce33f09d1cc50cb15e67c731f7548940cbc24
Reviewed-on: https://gerrit.chromium.org/gerrit/41103
Reviewed-by: Chris Sosa <sosa@chromium.org>
Commit-Queue: Jay Srinivasan <jaysri@chromium.org>
Tested-by: Jay Srinivasan <jaysri@chromium.org>
diff --git a/omaha_request_params.h b/omaha_request_params.h
index 7435468..ea8bab0 100644
--- a/omaha_request_params.h
+++ b/omaha_request_params.h
@@ -16,6 +16,9 @@
 
 namespace chromeos_update_engine {
 
+// The default "official" Omaha update URL.
+extern const char* const kProductionOmahaUrl;
+
 // This struct encapsulates the data Omaha gets for the request, along with
 // essential state needed for the processing of the request/response.
 // The strings in this struct should not be XML escaped.