Bug 1168606 - Added comments on almost-const data members r=ttung,asuth

Differential Revision: https://phabricator.services.mozilla.com/D42645

--HG--
extra : moz-landing-system : lando

dom/indexedDB/IDBCursor.h

@@ -58,6 +58,9 @@ class IDBCursor final : public nsISupports, public nsWrapperCache {
 
   indexedDB::BackgroundCursorChild* mBackgroundActor;
 
+  // TODO: mRequest, mSourceObjectStore and mSourceIndex could be made const if
+  // Bug 1575173 is resolved. They are initialized in the constructor and never
+  // modified/cleared.
   RefPtr<IDBRequest> mRequest;
   RefPtr<IDBObjectStore> mSourceObjectStore;
   RefPtr<IDBIndex> mSourceIndex;

dom/indexedDB/IDBIndex.h

@@ -35,6 +35,8 @@ class KeyPath;
 }  // namespace indexedDB
 
 class IDBIndex final : public nsISupports, public nsWrapperCache {
+  // TODO: This could be made const if Bug 1575173 is resolved. It is
+  // initialized in the constructor and never modified/cleared.
   RefPtr<IDBObjectStore> mObjectStore;
 
   JS::Heap<JS::Value> mCachedKeyPath;

dom/indexedDB/IDBObjectStore.h

@@ -54,6 +54,8 @@ class IDBObjectStore final : public nsISupports, public nsWrapperCache {
 
   static const JSClass sDummyPropJSClass;
 
+  // TODO: This could be made const if Bug 1575173 is resolved. It is
+  // initialized in the constructor and never modified/cleared.
   RefPtr<IDBTransaction> mTransaction;
   JS::Heap<JS::Value> mCachedKeyPath;