Add new "automatically send usage stats" setting under advanced setti…

…ngs.

By default, it's set to false; folks can opt-in by enabling it.

Fixes #4691

Auditors: @aekeus @bradleyrichter

Test Plan:
1. Open Brave and launch preferences
2. Go under advanced and see new setting (set to false)
3. Set to true and quit Brave
4. Relaunch Brave and open preferences > advanced
5. Setting should be persisted

app/extensions/brave/locales/en-US/preferences.properties

@@ -245,4 +245,5 @@ enableAutofill=Enable Autofill
 importBrowserData=Import Browser Data
 importNow=Import now…
 clearAll=Clear all
-sendCrashReports=Send anonymous crash reports to Brave (requires browser restart)
+sendCrashReports=Send anonymous crash reports to Brave (requires browser restart)
+sendUsageStatistics=Automatically send usage statistics to Brave

js/about/preferences.js

@@ -1501,6 +1501,7 @@ class AdvancedTab extends ImmutableComponent {
         <SettingCheckbox dataL10nId='usePDFJS' prefKey={settings.PDFJS_ENABLED} settings={this.props.settings} onChangeSetting={this.props.onChangeSetting} />
         <SettingCheckbox dataL10nId='useSmoothScroll' prefKey={settings.SMOOTH_SCROLL_ENABLED} settings={this.props.settings} onChangeSetting={this.props.onChangeSetting} />
         <SettingCheckbox dataL10nId='sendCrashReports' prefKey={settings.SEND_CRASH_REPORTS} settings={this.props.settings} onChangeSetting={this.props.onChangeSetting} />
+        <SettingCheckbox dataL10nId='sendUsageStatistics' prefKey={settings.SEND_USAGE_STATISTICS} settings={this.props.settings} onChangeSetting={this.props.onChangeSetting} />
       </SettingsList>
     </div>
   }

js/constants/appConfig.js

@@ -125,6 +125,7 @@ module.exports = {
     'advanced.pdfjs-enabled': true,
     'advanced.smooth-scroll-enabled': false,
     'advanced.send-crash-reports': true,
+    'advanced.send-usage-statistics': false,
     'advanced.minimum-visit-time': 8,
     'advanced.minimum-visits': 5,
     'shutdown.clear-history': false,

js/constants/settings.js

@@ -58,6 +58,7 @@ const settings = {
   DEFAULT_ZOOM_LEVEL: 'advanced.default-zoom-level',
   SMOOTH_SCROLL_ENABLED: 'advanced.smooth-scroll-enabled',
   SEND_CRASH_REPORTS: 'advanced.send-crash-reports',
+  SEND_USAGE_STATISTICS: 'advanced.send-usage-statistics',
   ADBLOCK_CUSTOM_RULES: 'adblock.customRules',
   MINIMUM_VISIT_TIME: 'advanced.minimum-visit-time',
   MINIMUM_VISTS: 'advanced.minimum-visits'