[fenix] Closes https://github.com/mozilla-mobile/fenix/issues/21424: add marker for StrictMode.resetAfter.

This helps identify file IO. Unfortunately, with this marker, it's
difficult to separate code we own from code we don't own. However, I
wasn't sure what the best implementation would be to address that
(e.g. ideally, we would ignore violations in code we don't own rather than
annotate the markers) so I thought we can land it this simple way and
improve it incrementally.

app/src/main/java/org/mozilla/fenix/perf/StrictModeManager.kt

@@ -113,6 +113,18 @@ class StrictModeManager(
      * @return the value returned by [functionBlock].
      */
     fun <R> resetAfter(policy: StrictMode.ThreadPolicy, functionBlock: () -> R): R {
+        fun instrumentedFunctionBlock(): R {
+            val startProfilerTime = components.core.engine.profiler?.getProfilerTime()
+
+            val returnValue = functionBlock()
+
+            if (mainLooper.thread === Thread.currentThread()) { // markers only supported on main thread.
+                components.core.engine.profiler?.addMarker("StrictMode.resetAfter", startProfilerTime)
+            }
+
+            return returnValue
+        }
+
         // Calling resetAfter takes 1-2ms (unknown device) so we only execute it if StrictMode can
         // actually be enabled. https://github.com/mozilla-mobile/fenix/issues/11617
         return if (isEnabledByBuildConfig) {
@@ -122,15 +134,11 @@ class StrictModeManager(
             val suppressionCount = suppressionCount.incrementAndGet()
 
             // We log so that devs are more likely to notice that we're suppressing StrictMode violations.
-            // We add profiler markers so that the perf team can easily identify IO locations in profiles.
             logger.warn("StrictMode violation suppressed: #$suppressionCount")
-            if (Thread.currentThread() == mainLooper.thread) { // markers only supported on main thread.
-                components.core.engine.profiler?.addMarker("StrictMode.suppression", "Count: $suppressionCount")
-            }
 
-            policy.resetAfter(functionBlock)
+            policy.resetAfter(::instrumentedFunctionBlock)
         } else {
-            functionBlock()
+            instrumentedFunctionBlock()
         }
     }