Settings reset prompt: add UMA metrics reporting.

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index da1f11b7838f7d0f76258be3bb670165f79d7615..90ecfd39293566399625c46c748461ea86c1b801 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -64126,6 +64126,82 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="SettingsResetPrompt.DefaultSearchResetState"
+    enum="SettingsResetPromptResetState">
+  <owner>alito@chromium.org</owner>
+  <summary>
+    Indicates whether the settings reset prompt is enabled for the user's
+    default search setting, or the reason for it being disabled.
+  </summary>
+</histogram>
+
+<histogram name="SettingsResetPrompt.DelayBeforePromptParam" units="seconds">
+  <owner>alito@chromium.org</owner>
+  <summary>
+    The feature parameter determining the amount of time to wait after startup
+    before attempting to show the settings reset prompt.
+  </summary>
+</histogram>
+
+<histogram name="SettingsResetPrompt.DialogState"
+    enum="SettingsResetPromptDialogState">
+  <owner>alito@chromium.org</owner>
+  <summary>
+    Indicates whether the settings reset prompt dialog was shown to the user and
+    how the user interacted with it.
+  </summary>
+</histogram>
+
+<histogram name="SettingsResetPrompt.ExtensionsToDisable" units="extensions">

[csharp, 2017/03/07 14:39:40]

nit: ExtensionsToDisable -> NumberOfExtensionsToDisable?

[alito, 2017/03/07 16:23:29]

Done.

+  <owner>alito@chromium.org</owner>
+  <summary>
+    The number of extensions that will be disabled if the user accepts the
+    settings reset prompt.
+  </summary>
+</histogram>
+
+<histogram name="SettingsResetPrompt.HomepageResetState"
+    enum="SettingsResetPromptResetState">
+  <owner>alito@chromium.org</owner>
+  <summary>
+    Indicates whether the settings reset prompt is enabled for the user's
+    homepage setting, or the reason for it being disabled.
+  </summary>
+</histogram>
+
+<histogram name="SettingsResetPrompt.PromptWanted" enum="Boolean">
+  <owner>alito@chromium.org</owner>
+  <summary>
+    Indicates whether the settings reset prompt should be shown to the user
+    based on the state of the user's settings.
+  </summary>
+</histogram>
+
+<histogram name="SettingsResetPrompt.StartupUrlsResetState"
+    enum="SettingsResetPromptResetState">
+  <owner>alito@chromium.org</owner>
+  <summary>
+    Indicates whether the settings reset prompt is enabled for the user's
+    startup pages setting, or the reason for it being disabled.
+  </summary>
+</histogram>
+
+<histogram name="SettingsResetPrompt.TimeUntilAccepted" units="ms">
+  <owner>alito@chromium.org</owner>
+  <summary>
+    The time between the settings reset prompt dialog being shown and the user
+    accepting the prompt.
+  </summary>
+</histogram>
+
+<histogram name="SettingsResetPrompt.TimeUntilDeclined" units="ms">
+  <owner>alito@chromium.org</owner>
+  <summary>
+    The time between the settings reset prompt dialog being shown and the user
+    declining the prompt.
+  </summary>
+</histogram>
+
 <histogram name="Setup.Install.ApplyArchivePatchTime" units="ms">
   <owner>grt@chromium.org</owner>
   <summary>
@@ -108521,6 +108597,22 @@ from previous Chrome versions.
   <int value="9" label="Bad time_between_prompts_seconds param"/>
 </enum>
 
+<enum name="SettingsResetPromptDialogState" type="int">
+  <int value="1" label="Shown"/>
+  <int value="2" label="Accepted"/>
+  <int value="3" label="Declined"/>
+</enum>
+
+<enum name="SettingsResetPromptResetState" type="int">
+  <int value="1" label="Reset required"/>
+  <int value="2" label="No reset required due to domain not matched"/>
+  <int value="3" label="No reset required due to already prompted for setting"/>
+  <int value="4" label="No reset required due to recently prompted"/>
+  <int value="5"
+      label="No reset required due to other setting requiring reset"/>
+  <int value="6" label="No reset required due to policy"/>
+</enum>
+
 <enum name="SettingsSections" type="int">
   <summary>
     A collection of sections from chrome://settings. Used for metrics about