mac: Expose keychain access frequency to Telemetry.

base/perf_util.cc

Index: base/perf_util.cc
diff --git a/base/perf_util.cc b/base/perf_util.cc
index 2d838a99b12fcf8f09abf281476235cc32860573..03af5207d06faf8b65b4f71ca35726a155ec7bef 100644
--- a/base/perf_util.cc
+++ b/base/perf_util.cc
@@ -4,6 +4,7 @@
 
 #include "base/perf_util.h"
 
+#include "base/metrics/histogram.h"
 #include "base/time/time.h"
 
 namespace base {
@@ -18,4 +19,8 @@ void SpinCpuMicroseconds(int64_t microseconds) {
   }

[jeremy, 2014/11/13 11:31:29]

Shouldn't be part of this CL.

[erikchen, 2014/11/13 22:52:59]

Right. I removed the dependency of this CL on the CL that added
SpinCpuMicroseconds.

 }
 
+void EmitAccessKeychainHistogram() {

[jeremy, 2014/11/13 11:31:29]

nit: rename IncrementKeychainAccessHistogram().

[erikchen, 2014/11/13 22:52:59]

Done.

+  LOCAL_HISTOGRAM_BOOLEAN("OSX.Keychain.Access", true);

[jeremy, 2014/11/13 11:31:29]

needs a comment here that explains what this histogram is, why we need it and
that it's read from Telemetry.

[erikchen, 2014/11/13 22:52:59]

I added copious documentation to the header file, which seemed like a better
location than the implementation file.

+}
+
 }  // namespace base