Fix up certificate error reporting histograms

chrome/browser/ssl/chrome_expect_ct_reporter.cc

Index: chrome/browser/ssl/chrome_expect_ct_reporter.cc
diff --git a/chrome/browser/ssl/chrome_expect_ct_reporter.cc b/chrome/browser/ssl/chrome_expect_ct_reporter.cc
index 14da6505d7153e123356f4ffbc6aef5c5b9e306e..a8ac0b0636c6a6d23d1121bf8d49c351fed3ca72 100644
--- a/chrome/browser/ssl/chrome_expect_ct_reporter.cc
+++ b/chrome/browser/ssl/chrome_expect_ct_reporter.cc
@@ -105,9 +105,9 @@ void AddValidSCT(const net::SignedCertificateTimestampAndStatus& sct_and_status,
 }
 
 // Records an UMA histogram of the net errors when Expect CT reports
-// fails to send.
+// fail to send.
 void RecordUMAOnFailure(const GURL& report_uri, int net_error) {
-  UMA_HISTOGRAM_SPARSE_SLOWLY("SSL.ExpectCTReportFailure", net_error);
+  UMA_HISTOGRAM_SPARSE_SLOWLY("SSL.ExpectCTReportFailure", -net_error);

[felt, 2016/07/01 22:05:58]

Will this change the histogram? Do you need to define a new histogram to avoid
messed up results in the transition?

[estark, 2016/07/01 22:08:53]

It will change it, but I think it's okay. I'm pretty sure I'm the only one
looking at these, and it just means that for a while we'll have to add two
numbers together (the negative version and the positive version) to get the full
count for a given error code. Maybe I should add a note to the histograms.xml
description?

[felt, 2016/07/01 22:13:48]

If you're the only one looking at it, probably fine, but please do add a note.

 }
 
 }  // namespace