docs($compileProvider): add more info on debugInfoEnabled()

Add more info on what `debugInfoEnabled()` affects.

Closes angular#16154

Author: oBusk

src/ng/compile.js

@@ -1387,7 +1387,12 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
    * binding information and a reference to the current scope on to DOM elements.
    * If enabled, the compiler will add the following to DOM elements that have been bound to the scope
    * * `ng-binding` CSS class
+   * * `ng-scope` and `ng-isolated-scope` CSS classes
    * * `$binding` data property containing an array of the binding expressions
+   * * Data properties used by the {@link angular.element#methods `scope()`/`isolateScope()` methods} to return
+   *   the element's scope.
+   * * Placeholder comments will contain information about what directive and binding caused the placeholder.
+   *   E.g. `<!-- ngIf: shouldShow() -->`.
    *
    * You may want to disable this in production for a significant performance boost. See
    * {@link guide/production#disabling-debug-data Disabling Debug Data} for more.