For 11660: fixing nits for previous #11668 (#11821)

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

@@ -257,8 +257,9 @@ open class FenixApplication : LocaleAwareApplication(), Provider {
         // no-op, LeakCanary is disabled by default
     }
 
-    // This is for issue https://github.com/mozilla-mobile/fenix/issues/11660. We prefetch our info for startup
-    // so that we're sure that we have all the data available as our fragment is launched.
+    /**
+     * See [TopsiteStore.prefetch] for details on pre fetching.
+     */
     private fun prefetchForHomeFragment() {
         StrictMode.allowThreadDiskReads().resetPoliciesAfter {
             components.core.topSiteStorage.prefetch()

app/src/main/java/org/mozilla/fenix/components/TopSiteStorage.kt

@@ -14,7 +14,7 @@ import mozilla.components.feature.top.sites.TopSite
 import mozilla.components.feature.top.sites.TopSiteStorage
 import mozilla.components.support.locale.LocaleManager
 import org.mozilla.fenix.R
-import org.mozilla.fenix.ext.observeOnce
+import org.mozilla.fenix.ext.observeOnceAndRemoveObserver
 import org.mozilla.fenix.ext.settings
 import org.mozilla.fenix.settings.SupportUtils
 import org.mozilla.fenix.settings.advanced.getSelectedLocale
@@ -88,8 +88,15 @@ class TopSiteStorage(private val context: Context) {
         }
     }
 
+    /**
+     * This is for issue https://github.com/mozilla-mobile/fenix/issues/11660. We prefetch the top
+     * sites for startup so that we're sure that we have all the data available as our fragment is
+     * launched to make sure that we can display everything on the home screen on the first drawing pass.
+     * This method doesn't negatively affect performance since the [getTopSites] runs on the a
+     * background thread.
+     */
     fun prefetch() {
-        getTopSites().observeOnce {
+        getTopSites().observeOnceAndRemoveObserver {
             cachedTopSites = it
         }
     }

app/src/main/java/org/mozilla/fenix/ext/LiveData.kt

@@ -10,11 +10,11 @@ import androidx.lifecycle.Observer
 /**
  * Observe a LiveData once and unregister from it as soon as the live data returns a value
  */
-fun <T> LiveData<T>.observeOnce(observer: (T) -> Unit) {
+fun <T> LiveData<T>.observeOnceAndRemoveObserver(callback: (T) -> Unit) {
     observeForever(object : Observer<T> {
         override fun onChanged(value: T) {
             removeObserver(this)
-            observer(value)
+            callback(value)
         }
     })
 }