Refactor asCamelCase to use string builder (#6141)

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

@@ -47,15 +47,31 @@ private class EventWrapper<T : Enum<T>>(
     private val recorder: ((Map<T, String>?) -> Unit),
     private val keyMapper: ((String) -> T)? = null
 ) {
-    private val String.asCamelCase: String
-        get() = this.split("_").reduceIndexed { index, acc, s ->
-            if (index == 0) acc + s
-            else acc + s.capitalize()
+
+    /**
+     * Converts snake_case string to camelCase.
+     */
+    private fun String.asCamelCase(): String {
+        val parts = split("_")
+        val builder = StringBuilder()
+
+        for ((index, part) in parts.withIndex()) {
+            if (index == 0) {
+                builder.append(part)
+            } else {
+                builder.append(part[0].toUpperCase())
+                builder.append(part.substring(1))
+            }
         }
 
+        return builder.toString()
+    }
+
     fun track(event: Event) {
         val extras = if (keyMapper != null) {
-            event.extras?.mapKeys { keyMapper.invoke(it.key.toString().asCamelCase) }
+            event.extras?.mapKeys { (key) ->
+                keyMapper.invoke(key.toString().asCamelCase())
+            }
         } else {
             null
         }

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

@@ -297,7 +297,7 @@ sealed class Event {
         }
 
         override val extras: Map<Events.browserMenuActionKeys, String>?
-            get() = mapOf(Events.browserMenuActionKeys.item to item.toString().toLowerCase())
+            get() = mapOf(Events.browserMenuActionKeys.item to item.toString().toLowerCase(Locale.ROOT))
     }
 
     sealed class Search