Settings reset prompt: add UMA metrics reporting.

chrome/browser/safe_browsing/settings_reset_prompt/settings_reset_prompt_model.cc

Index: chrome/browser/safe_browsing/settings_reset_prompt/settings_reset_prompt_model.cc
diff --git a/chrome/browser/safe_browsing/settings_reset_prompt/settings_reset_prompt_model.cc b/chrome/browser/safe_browsing/settings_reset_prompt/settings_reset_prompt_model.cc
index d4025848575f2a05ac8bbc4c7e470622618f9f19..d84e3c69e291448d48acdbacf04dcff5f1513b4a 100644
--- a/chrome/browser/safe_browsing/settings_reset_prompt/settings_reset_prompt_model.cc
+++ b/chrome/browser/safe_browsing/settings_reset_prompt/settings_reset_prompt_model.cc
@@ -8,6 +8,7 @@
 
 #include "base/bind_helpers.h"
 #include "base/callback.h"
+#include "base/metrics/histogram_macros.h"
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/google/google_brand.h"
 #include "chrome/browser/prefs/session_startup_pref.h"
@@ -276,6 +277,22 @@ SettingsResetPromptModel::extensions_to_disable() const {
   return extensions_to_disable_;
 }
 
+void SettingsResetPromptModel::ReportUmaMetrics() const {
+  UMA_HISTOGRAM_BOOLEAN("SettingsResetPrompt.PromptWanted",
+                        ShouldPromptForReset());
+  UMA_HISTOGRAM_ENUMERATION("SettingsResetPrompt.DefaultSearchResetState",
+                            default_search_reset_state(), RESET_STATE_MAX);
+  UMA_HISTOGRAM_ENUMERATION("SettingsResetPrompt.StartupUrlsResetState",
+                            startup_urls_reset_state(), RESET_STATE_MAX);
+  UMA_HISTOGRAM_ENUMERATION("SettingsResetPrompt.HomepageResetState",
+                            homepage_reset_state(), RESET_STATE_MAX);
+  UMA_HISTOGRAM_SPARSE_SLOWLY("SettingsResetPrompt.NumberOfExtensionsToDisable",

[jwd, 2017/03/07 18:08:37]

I'm not super keen on this being sparse, since it can have arbitrary values
(determined by the client). Although in this case it's not a problem on the
client, and will be more memory efficient than a count histogram, when
aggregating during analysis, the histogram becomes arbitrarily large, causing
problems.

Do you need exact numbers for each emit? Using a count histogram will give you
an exact sum when aggregating, and the distribution.

[alito, 2017/03/07 20:42:05]

Changed this to a count histogram. I think that will work just as well for this
case. Thx.

+                              extensions_to_disable().size());
+  UMA_HISTOGRAM_SPARSE_SLOWLY(
+      "SettingsResetPrompt.DelayBeforePromptParam",
+      prompt_config_->delay_before_prompt().InSeconds());
+}
+
 // static
 void SettingsResetPromptModel::OnSettingsFetched(
     Profile* profile,