android_isolated_splits.md: Update that b/172602571 is not fixed.

Change-Id: Ia26a022859178ed93b63e8bfcdb46e8ee62ca10f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3714278
Auto-Submit: Andrew Grieve <[email protected]>
Commit-Queue: Clark DuVall <[email protected]>
Reviewed-by: Clark DuVall <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1016198}
diff --git a/docs/android_isolated_splits.md b/docs/android_isolated_splits.md
index 48cad9e..f2c90b0 100644
--- a/docs/android_isolated_splits.md
+++ b/docs/android_isolated_splits.md
@@ -101,14 +101,15 @@
 [preemptively run]: https://source.chromium.org/search?q=symbol:DexFixer.needsDexCompile&ss=chromium
 [PackageReplacedBroadcastReceiver]: https://source.chromium.org/search?q=symbol:PackageReplacedBroadcastReceiver&ss=chromium
 
-### Conflicting ClassLoaders (Android Pre-S)
+### Conflicting ClassLoaders
 
 Missing synchronization can cause the parent ClassLoader of split contexts to
 be different from the Application's ClassLoader. This manifests as odd-looking
 `ClassCastExceptions` where `"TypeA cannot be cast to TypeA"` (since the two
 `TypeAs` are from different ClassLoaders).
 
-Fixed in Android S. Bug: [b/172602571] (Googler only).
+Tracked by UMA `Android.IsolatedSplits.ClassLoaderReplaced`. Occurs < 0.05% of
+the time.
 
 **Work-around:**