Delete the PreferenceMACs on profile deletion.

components/prefs/testing_pref_store.cc

Index: components/prefs/testing_pref_store.cc
diff --git a/components/prefs/testing_pref_store.cc b/components/prefs/testing_pref_store.cc
index efdc83fcc7776eb37d2c4c9c625272ede3516a53..8b1524a2d7c53e17f516a362e7698126f09a0ed3 100644
--- a/components/prefs/testing_pref_store.cc
+++ b/components/prefs/testing_pref_store.cc
@@ -179,6 +179,10 @@ void TestingPrefStore::ClearMutableValues() {
   NOTIMPLEMENTED();
 }
 
+void TestingPrefStore::OnStoreDeletionFromDisk() {
+  NOTIMPLEMENTED();

[gab, 2017/06/08 16:14:28]

That results in a log warning, in this case I think the right impl is actually
an empty body, so remove NOTIMPLEMENTED()

[proberge, 2017/06/08 18:32:59]

Done.

+}
+
 void TestingPrefStore::set_read_only(bool read_only) {
   read_only_ = read_only;
 }