Adding support for sampling crashes in Chrome on Windows.

chrome/install_static/install_util.h

Index: chrome/install_static/install_util.h
diff --git a/chrome/install_static/install_util.h b/chrome/install_static/install_util.h
index be2a99d4751a49c8509b9b5559afe9b048bcb455..22db14a5fc062dfb2dc0a895bd3311962bd9d300 100644
--- a/chrome/install_static/install_util.h
+++ b/chrome/install_static/install_util.h
@@ -41,6 +41,14 @@ extern const wchar_t kAppGuidCanary[];
 extern const wchar_t kAppGuidGoogleChrome[];
 extern const wchar_t kAppGuidGoogleBinaries[];
 
+// Registry key to store the stats/crash sampling state of Chrome. If set to 1,
+// stats and crash reports will be uploaded in line with the user's consent,
+// otherwise, uploads will be dissabled. It is used to sample clients, to reduce

[robertshield, 2016/08/12 17:49:25]

s/dissabled/disabled/

[jwd, 2016/08/12 20:04:31]

Done.

+// server load for metics and crashes. This is controlled by the
+// MetricsReporting feature in chrome_metrics_services_manager_client.cc and is
+// written when metrics services are started up and when consent changes.
+extern const wchar_t kChromeStatsSampleKey[];

[Alexei Svitkine (slow), 2016/08/12 17:47:48]

Since this is no longer used outside of the .cc file, I would remove it from the
.h file and put it in an anon namespace in the .cc file with the comment.

[robertshield, 2016/08/12 17:49:25]

What is the relationship between the value stored here and the value stored at
kRegValueUsageStats which also seems to control UMA and crash reporting?

[jwd, 2016/08/12 20:04:30]

Done.

[jwd, 2016/08/12 20:04:31]

kRegValueUsageStats is the source of consent described in the above comment.
I've added a comment to that const.

+
 // TODO(ananta)
 // https://crbug.com/604923
 // Unify these constants with env_vars.h.
@@ -78,6 +86,14 @@ bool GetCollectStatsConsent();
 // Only used by tests.
 bool GetCollectStatsConsentForTesting(const std::wstring& exe_path);
 
+// Returns true if the current executable is currently in the chosen sample that
+// will report stats and crashes.
+bool GetCollectStatsInSample();
+
+// Sets the registry value used for checking if Chrome is in the chosen sample
+// that will report stats and crashes. Returns true if writing was successful.
+bool SetCollectStatsInSample(bool in_sample);
+
 // Returns true if if usage stats reporting is controlled by a mandatory
 // policy. |metrics_is_enforced_by_policy| will be set to true accordingly.
 // TODO(ananta)