message: Add some memory leak tips to my notes.
diff: @@ -18,3 +18,13 @@ Clean up TODO
  * Move to the Custom Elements v1 spec. No more registerElement(). (Need Electron 1.6 and an updated nodejs.)
  * Eliminate the init() thing in the elements.
  +
  +Memory Leaks: Lessons Learnt
  +============================
  +
  +Known Bug: lit-html memory leak: https://github.com/Polymer/lit-html/issues/1416
  +Tip: `Detached ShadowRoots` are useful for finding our custom elements.
  +Tip: Mark interesting elements with a 'time' child node. It is easy to find in the memory debugger.
  +Tip: Closures can easily generate memory leaks. => Closure scope should be restricted and limited.
  +Tip: `WeakMap` can generate a memory leak if the `value` has a reference to the `key`.
  +Tip: If you print an object directly into `console.log()` then the console viewer will hold a reference to that object.
  