Add property reflection for Polymer computed properties and observers

[ChadKillingsworth]

Polymer observers and computed properties use string reflection. When property renaming is enabled, add property reflection calls to these strings such that they are renamed consistently.

Example:

class FooElement extends Polymer.Element {
  static get properties() {
    return {
      foo: {
        type: String,
        compute: '_computeFoo(bar)'
      },
      bar: {
        type: String,
        value: 'bar'
      }
    };
  }
  _computeFoo(bar) {
    return 'foo' + bar;
   }
}

The '_computeFoo(bar)' string will now be parsed and reflection calls added like:

JSCompiler_renameProperty('_computeFoo', /** @type {!FooElement} */ ({})) + '(' +
    JSCompiler_renameProperty('bar', /** @type {!FooElement} */ ({})) + ')'

[ChadKillingsworth]

cc @aomarks

[lauraharker]

Internal issue http://b/122359057 created

[aomarks]

This is great!

[ChadKillingsworth]

I'm on vacation this week. I'll address the feedback next week.

[ChadKillingsworth]

@aomarks I've made the changes you requested

[lauraharker]

Importing for internal review

[ChadKillingsworth]

@lauraharker @aomarks I have been unable to recreate the remaining issue. I've re-arranged the code a bit on a hunch and also updated the source references so that the warning should point to what exactly is triggering the warning.

If you can try this again with the latest changes, that will at least help me narrow down what's causing the type warning. It's a bit odd because I'm not changing any type signatures with this code.

[lauraharker]

@ChadKillingsworth here's the new warning I get:

polymer/v2/polymer/lib/elements/array-selector.js:51: ERROR - variable ArraySelectorMixin.prototype.items redefined with type (Array|null), original definition at polymer/v2/polymer/lib/elements/array-selector.js:59 with type Array
  class ArraySelectorMixin extends elementBase {
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Here's array-selector.js immediately after the PolymerPass with --pretty_print and --preserve_type_annotations:
array-selector-after-polymer.txt

[ChadKillingsworth]

Thanks - that helps.

Here's my best guess: the compiler is treating the Element.prototype.propName; statements being used for a property sink as a nullability redefinition. That's surprising to me, but at least plausible.

I've refactored the code to add the synthetic sink statements directly rather than relying on the CheckSideEffects pass to add them. Hopefully this will solve the issue.

[lauraharker]

That fixed it!

I'm running another set of internal tests now.

[lauraharker]

Or no, that was a false positive.

I now get a different error:

{SyntheticVarsDeclar}: ERROR - Variable JSCOMPILER_PRESERVE declared more than once. First occurrence: {SyntheticVarsDeclar}

[lauraharker]

The latest commit fixes the error I was seeing. 👍
I'm doing another round of global testing now.

[lauraharker]

Submitting this change internally