Test:
1. Build the Chrome extension and load it.
2. Visit https://robwu.nl/pdfjs/object-embed.html
3. Verify that all displayed blocks have the same width and
height as the reference ("Expected dimension").
Multiple shadow roots are not supported any more in Chrome 51+
(https://crbug.com/603448#c6), so this patch changes the way that PDFs
are rendered in `<embed>` / `<object>` tags.
I used shadow roots because their content is not visible from the web
page, so the odds of conflicts were minimal. Now I have to render the
PDF frame directly in the page, which can be observed from the page
(unfortunately).
Now the following happens when an embedded PDF tag is detected:
- `<embed>` tags: The type and src attributes are updated.
- `<object>` tags: The type attribute is changed and the fallback
content is set and displayed.
As explained in
https://github.com/mozilla/pdf.js/issues/6174#issuecomment-118502802.
To verify that this patch works:
1. Build the Chrome extension (node make chromium)
2. Load the Chrome extension (at chrome://extensions)
3. Visit https://robwu.nl/pdfjs/issue6174/.
4. Verify that PDF.js is not used to load the PDF. Either Chrome's
default PDF Viewer is used, or the PDF is offered as a file download.
document.documentElement.style is null in some XML documents.
The previous snippet caused the following error:
Uncaught TypeError: Cannot use 'in' operator to search for 'animation' in null
To fix this bug, `'animation' in document.documentElement.style` has been
replaced with `CSS.supports('animation', '9s')`. This method was introduced
in Chromium 28, but it is not necessary to detect whether this method is
supported because the required createShadowRoot method for embeds is not
available in Chromium 32 and earlier.
