[fenix] Closes https://github.com/mozilla-mobile/fenix/issues/7762: Initialize Glean later in Fennec builds.

app/src/main/java/org/mozilla/fenix/Config.kt

@@ -57,6 +57,9 @@ enum class ReleaseChannel {
 
     val isFennec: Boolean
         get() = this in fennecChannels
+
+    val isFenix: Boolean
+        get() = !isFennec
 }
 
 object Config {

app/src/main/java/org/mozilla/fenix/FenixApplication.kt

@@ -59,21 +59,22 @@ open class FenixApplication : LocaleAwareApplication() {
             return
         }
 
-        // We need to always initialize Glean and do it early here.
-        // It is important that this initialization happens *here* before calling into
-        // setupInMainProcessOnly() which behaves differently for fenix and fennec builds.
-        val enableGlean = if (Config.channel.isFennec) {
-            // We are disabling Glean here because for Fennec builds we may not know yet whether
-            // we can enable telemetry yet. We first need to migrate the setting from Fennec to
-            // know the user's choice. The blocking migration in `MigratingFenixApplication` will
-            // notify glean once the value has been migrated.
-            false
-        } else {
-            // We initialize Glean with telemetry enabled (or disabled) early here so that we do not
-            // end up loosing data for components that collect telemetry very early.
-            settings().isTelemetryEnabled
+        if (Config.channel.isFenix) {
+            // We need to always initialize Glean and do it early here.
+            // Note that we are only initializing Glean here for "fenix" builds. "fennec" builds
+            // will initialize in MigratingFenixApplication because we first need to migrate the
+            // user's choice from Fennec.
+            initializeGlean()
         }
-        logger.debug("Initializing Glean (uploadEnabled=$enableGlean, isFennec=${Config.channel.isFennec})")
+
+        setupInMainProcessOnly()
+    }
+
+    protected fun initializeGlean() {
+        val telemetryEnabled = settings().isTelemetryEnabled
+
+        logger.debug("Initializing Glean (uploadEnabled=$telemetryEnabled, isFennec=${Config.channel.isFennec})")
+
         Glean.initialize(
             applicationContext = this,
             configuration = Configuration(
@@ -81,10 +82,8 @@ open class FenixApplication : LocaleAwareApplication() {
                 httpClient = ConceptFetchHttpUploader(
                     lazy(LazyThreadSafetyMode.NONE) { components.core.client }
                 )),
-            uploadEnabled = enableGlean
+            uploadEnabled = telemetryEnabled
         )
-
-        setupInMainProcessOnly()
     }
 
     @CallSuper

app/src/migration/java/org/mozilla/fenix/MigratingFenixApplication.kt

@@ -38,6 +38,10 @@ class MigratingFenixApplication : FenixApplication() {
         // These migrations need to run before regular initialization happens.
         migrateBlocking()
 
+        // Now that we have migrated from Fennec whether the user wants to enable telemetry we can
+        // initialize Glean
+        initializeGlean()
+
         // Fenix application initialization can happen now.
         super.setupInMainProcessOnly()