<object> / <embed> support in Chrome / Opera

This PR brings support for embedded PDFs of the following forms:

```
<object type="application/pdf" data="...">
<embed type="application/pdf" src="...">
<object data="....pdf"> <!-- note: no type specified -->
<embed src="....pdf"> <!-- note: no type specified -->
```

Fixes https://github.com/operasoftware/pdf.js/issues/19
Fixes #3736
Supersedes #4194

##### Tests
To check whether the feature works as intended, visit the following pages, and check whether the PDF viewer is rendered:

- http://plugindoc.mozdev.org/testpages/pdf.html
- http://acroeng.adobe.com/wp/?page_id=161 (all 9 examples)
- http://pdfpiw.uspto.gov/.piw?Docid=08000431&homeurl=http%3A%2F%2Fpatft.uspto.gov%2Fnetacgi%2Fnph-Parser%3FSect1%3DPTO2%2526Sect2%3DHITOFF%2526p%3D1%2526u%3D%25252Fnetahtml%25252FPTO%25252Fsearch-bool.html%2526r%3D1%2526f%3DG%2526l%3D50%2526co1%3DAND%2526d%3DPTXT%2526s1%3D3,257,285%2526OS%3D3,257,285%2526RS%3D3,257,285&PageNum=&Rtype=&SectionNum=&idkey=NONE&Input=View+first+page

##### Performance profiling
This PR consists of two commits. The first one introduces the feature, together with tools used to profile the performance of the implementation. The second commit removes these tools.
If you want to test the performance yourself, simply revert the second commit, build the Chromium extension and browse pages on the internet. The tool shows a dialog with load time statistics after page load.