Set `distributionId` right after initializing Glean

Previously setting it might have been arbitrarily delayed, resulting in
this metrics missing from pings that get submitted earlier.
Setting it early should prevent that.
The performance impact is negligible, Glean dispatches recording that
data off-main-thread anyway.

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

@@ -40,6 +40,7 @@ import mozilla.components.support.rustlog.RustLog
 import mozilla.components.support.utils.logElapsedTime
 import mozilla.components.support.webextensions.WebExtensionSupport
 import org.mozilla.fenix.GleanMetrics.GleanBuildInfo
+import org.mozilla.fenix.GleanMetrics.Metrics
 import org.mozilla.fenix.GleanMetrics.PerfStartup
 import org.mozilla.fenix.components.Components
 import org.mozilla.fenix.components.metrics.MetricServiceType
@@ -115,6 +116,14 @@ open class FenixApplication : LocaleAwareApplication(), Provider {
             uploadEnabled = telemetryEnabled,
             buildInfo = GleanBuildInfo.buildInfo
         )
+
+        // Set this early to guarantee it's in every ping from here on.
+        Metrics.distributionId.set(
+            when (Config.channel.isMozillaOnline) {
+                true -> "MozillaOnline"
+                false -> "Mozilla"
+            }
+        )
     }
 
     @CallSuper

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

@@ -12,7 +12,6 @@ import mozilla.components.service.fxa.manager.SyncEnginesStorage
 import mozilla.components.service.glean.Glean
 import mozilla.components.service.glean.private.NoExtraKeys
 import mozilla.components.support.base.log.logger.Logger
-import org.mozilla.fenix.Config
 import org.mozilla.fenix.GleanMetrics.AboutPage
 import org.mozilla.fenix.GleanMetrics.Addons
 import org.mozilla.fenix.GleanMetrics.AppTheme
@@ -848,13 +847,6 @@ class GleanMetricsService(
                 defaultMozBrowser.set(it)
             }
 
-            distributionId.set(
-                when (Config.channel.isMozillaOnline) {
-                    true -> "MozillaOnline"
-                    false -> "Mozilla"
-                }
-            )
-
             mozillaProducts.set(mozillaProductDetector.getInstalledMozillaProducts(context))
 
             adjustCampaign.set(context.settings().adjustCampaignId)