Garbage Collect the Storage directory on next profile start after an extension uninstall.

chrome/common/pref_names.cc

Index: chrome/common/pref_names.cc
diff --git a/chrome/common/pref_names.cc b/chrome/common/pref_names.cc
index 952b040e8c7d2ed284edbccdd64ee58c5530f27d..fef449744bf2a60dfad91bbcd57e9ab51b2e4a59 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -1529,6 +1529,11 @@ const char kNextExtensionsUpdateCheck[] = "extensions.autoupdate.next_check";
 const char kExtensionBlacklistUpdateVersion[] =
     "extensions.blacklistupdate.version";
 
+// Indicates on-disk data might have skeletal data that needs to be cleaned
+// on the next start of the browser.
+const char kExtensionStorageGarbageCollect[] =
+    "extensions.storage.garbagecollect";
+
 // Keeps track of which sessions are collapsed in the Other Devices menu.
 const char kNtpCollapsedForeignSessions[] = "ntp.collapsed_foreign_sessions";