Merge branch 'jr/amp-addthis' of https://github.com/dmvjs/amphtml int…

…o jr/amp-addthis

* 'jr/amp-addthis' of https://github.com/dmvjs/amphtml: (54 commits)
  Add required logic for view/engagement analytics without an iframe
  Lojson call refactor; saving WIP
  Code review cleanup
  Make all images in AMP have the `async` attribute. (ampproject#11366)
  skip test (ampproject#11459)
  Fix having multiple Criteo standalone ads on one page (ampproject#11285)
  add `bt` (binary type) query param to error reporting query string (ampproject#11452)
  Enables vendor iframe to send response to creative (ampproject#11306)
  Remove noisy 3p error for user error reporting (ampproject#11382)
  Ramp Fast Fetch crypto verifier experiment to 10% (ampproject#11447)
  Updates doubleclick impl to include docs on fluid (ampproject#11437)
  Revert "Add a visual diff test for amp-pinterest" (ampproject#11442)
  Ramp experiment down to 0 (ampproject#11441)
  Updated changelog with recent validator release (ampproject#11440)
  Remove pfx parameter from Doubleclick Fast Fetch reuests (ampproject#11439)
  Allow element to accept custom share attributes (with fallback); remove other ownerDocument refs
  Add wait code for amp.article.html (ampproject#11429)
  fix inabox-viewport test (ampproject#11428)
  Remove camelcase from data attributes
  Amp Ad Fast Fetch allow amp-image prefetch (ampproject#11391)
  ...