For #15644: add comment for why we set the app theme in test.

app/src/test/java/org/mozilla/fenix/helpers/FenixRobolectricTestApplication.kt

@@ -17,7 +17,7 @@ class FenixRobolectricTestApplication : FenixApplication() {
 
     override fun onCreate() {
         super.onCreate()
-        setTheme(R.style.NormalTheme)
+        setApplicationTheme()
     }
 
     override val components = TestComponents(this)
@@ -27,4 +27,14 @@ class FenixRobolectricTestApplication : FenixApplication() {
     override fun setupInAllProcesses() = Unit
 
     override fun setupInMainProcessOnly() = Unit
+
+    private fun setApplicationTheme() {
+        // According to the Robolectric devs, the application context will not have the <application>'s
+        // theme but will use the platform's default team so we set our theme here. We change it here
+        // rather than the production application because, upon testing, the production code appears
+        // appears to be working correctly. Context here:
+        // https://github.com/mozilla-mobile/fenix/pull/15646#issuecomment-707345798
+        // https://github.com/mozilla-mobile/fenix/pull/15646#issuecomment-709411141
+        setTheme(R.style.NormalTheme)
+    }
 }