GitLab

Tests affected:
PDFExtensionTest.Basic
PDFExtensionTest.Bookmark
PDFExtensionTest.Elements
PDFExtensionTest.ToolbarManager

Most of the fixes involve adding Custom Elements to be tested in the document,
otherwise their local DOM is not populated (unlike Polymer 1).

Bug: 849476
Change-Id: Id953179142174cb5922bf53bcaa139011ea76ca9
Reviewed-on: https://chromium-review.googlesource.com/1100304Reviewed-by: Rebekah Potter <rbpotter@chromium.org>
Commit-Queue: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567312}