For #18608 Add experiment for set default browser MenuItem.

app/src/main/java/org/mozilla/fenix/components/metrics/Event.kt

@@ -582,7 +582,7 @@ sealed class Event {
             NEW_PRIVATE_TAB, SHARE, BACK, FORWARD, RELOAD, STOP, OPEN_IN_FENIX,
             SAVE_TO_COLLECTION, ADD_TO_TOP_SITES, ADD_TO_HOMESCREEN, QUIT, READER_MODE_ON,
             READER_MODE_OFF, OPEN_IN_APP, BOOKMARK, READER_MODE_APPEARANCE, ADDONS_MANAGER,
-            BOOKMARKS, HISTORY, SYNC_TABS, DOWNLOADS
+            BOOKMARKS, HISTORY, SYNC_TABS, DOWNLOADS, SET_DEFAULT_BROWSER
         }
 
         override val extras: Map<Events.browserMenuActionKeys, String>?

app/src/main/java/org/mozilla/fenix/components/toolbar/BrowserToolbarMenuController.kt

@@ -41,6 +41,7 @@ import org.mozilla.fenix.ext.components
 import org.mozilla.fenix.ext.getRootView
 import org.mozilla.fenix.ext.nav
 import org.mozilla.fenix.ext.navigateSafe
+import org.mozilla.fenix.ext.openSetDefaultBrowserOption
 import org.mozilla.fenix.settings.deletebrowsingdata.deleteAndQuit
 import org.mozilla.fenix.utils.Do
 import org.mozilla.fenix.utils.Settings
@@ -338,6 +339,9 @@ class DefaultBrowserToolbarMenuController(
                     BrowserFragmentDirections.actionGlobalHome(focusOnAddressBar = true)
                 )
             }
+            is ToolbarMenu.Item.SetDefaultBrowser -> {
+                activity.openSetDefaultBrowserOption()
+            }
         }
     }
 
@@ -387,6 +391,7 @@ class DefaultBrowserToolbarMenuController(
             is ToolbarMenu.Item.History -> Event.BrowserMenuItemTapped.Item.HISTORY
             is ToolbarMenu.Item.Downloads -> Event.BrowserMenuItemTapped.Item.DOWNLOADS
             is ToolbarMenu.Item.NewTab -> Event.BrowserMenuItemTapped.Item.NEW_TAB
+            is ToolbarMenu.Item.SetDefaultBrowser -> Event.BrowserMenuItemTapped.Item.SET_DEFAULT_BROWSER
         }
 
         metrics.track(Event.BrowserMenuItemTapped(eventItem))

app/src/main/java/org/mozilla/fenix/components/toolbar/DefaultToolbarMenu.kt

@@ -38,10 +38,14 @@ import org.mozilla.fenix.FeatureFlags
 import org.mozilla.fenix.HomeActivity
 import org.mozilla.fenix.R
 import org.mozilla.fenix.browser.browsingmode.BrowsingMode
+import org.mozilla.fenix.experiments.ExperimentBranch
+import org.mozilla.fenix.experiments.Experiments
 import org.mozilla.fenix.ext.asActivity
 import org.mozilla.fenix.ext.components
 import org.mozilla.fenix.ext.settings
+import org.mozilla.fenix.ext.withExperiment
 import org.mozilla.fenix.theme.ThemeManager
+import org.mozilla.fenix.utils.BrowsersCache
 
 /**
  * Builds the toolbar object used with the 3-dot menu in the browser fragment.
@@ -357,6 +361,7 @@ open class DefaultToolbarMenu(
             BrowserMenuDivider(),
             reportSiteIssuePlaceholder,
             findInPage,
+            getSetDefaultBrowserItem(),
             addToTopSites,
             addToHomescreen.apply { visible = ::canAddToHomescreen },
             installToHomescreen.apply { visible = ::canInstall },
@@ -594,4 +599,21 @@ open class DefaultToolbarMenu(
                 .any { it.url == newUrl }
         }
     }
+    private fun getSetDefaultBrowserItem(): BrowserMenuImageText? {
+        val experiments = context.components.analytics.experiments
+        val browsers = BrowsersCache.all(context)
+
+        return experiments.withExperiment(Experiments.DEFAULT_BROWSER) { experimentBranch ->
+            if (experimentBranch == ExperimentBranch.DEFAULT_BROWSER_TOOLBAR_MENU && !browsers.isDefaultBrowser) {
+                return@withExperiment BrowserMenuImageText(
+                    label = context.getString(R.string.preferences_set_as_default_browser),
+                    imageResource = R.mipmap.ic_launcher
+                ) {
+                    onItemTapped.invoke(ToolbarMenu.Item.SetDefaultBrowser)
+                }
+            } else {
+                null
+            }
+        }
+    }
 }

app/src/main/java/org/mozilla/fenix/components/toolbar/ToolbarMenu.kt

@@ -26,6 +26,7 @@ interface ToolbarMenu {
         object AddonsManager : Item()
         object Quit : Item()
         object OpenInApp : Item()
+        object SetDefaultBrowser : Item()
         object Bookmark : Item()
         object CustomizeReaderView : Item()
         object Bookmarks : Item()

app/src/main/java/org/mozilla/fenix/experiments/Experiments.kt

@@ -9,6 +9,7 @@ class Experiments {
         const val A_A_NIMBUS_VALIDATION = "fenix-nimbus-validation-v3"
         const val BOOKMARK_ICON = "fenix-bookmark-list-icon"
         const val ANDROID_KEYSTORE = "fenix-android-keystore"
+        const val DEFAULT_BROWSER = "fenix-default-browser"
     }
 }
 
@@ -18,5 +19,6 @@ class ExperimentBranch {
         const val CONTROL = "control"
         const val A1 = "a1"
         const val A2 = "a2"
+        const val DEFAULT_BROWSER_TOOLBAR_MENU = "default_browser_toolbar_menu"
     }
 }