PDF loaded using pdfium when PDFJS isn't downloaded

[srirambv]

Description

PDF loaded using pdfium when PDFJS isn't downloaded

Steps to Reproduce

1. Clean profile on Beta , open chrome://extensions, no PDFJS installed (PDFJS not installed by default #1375)
2. Visit http://orimi.com/pdf-test.pdf, PDF is loaded in the tab,
3. Right click on PDF and inspect, shows

<embed id="plugin" type="application/x-google-chrome-pdf" src="http://orimi.com/pdf-test.pdf" stream-url="blob:chrome-extension://mhjfbmdgcfjbbpaeojofohoefgiehjai/55285240-5879-4950-96fe-2c7afe71af08" 

Actual result:

PDF is loaded in a tab even if browser fails to install PDFJS at start

Expected result:

Should not use PDFIUM to load PDF files when PDFJS is not installed/disabled

Reproduces how often:

Easy

Brave version (chrome://version info)

Brave	0.55.10 Chromium: 70.0.3538.22 (Official Build) beta (64-bit)
Revision	ac9418ba9c3bd7f6baaffa0b055dfe147e0f8364-refs/branch-heads/3538@{#468}
OS	All

Reproducible on current release:

• Does it reproduce on brave-browser dev/beta builds?
• Does it reproduce on browser-laptop?

Website problems only:

• Does the issue resolve itself when disabling Brave Shields?
• Is the issue reproducible on the latest version of Chrome?

Additional Information

cc: @bbondy

[LaurenWags]

Verified using

Brave	0.55.11 Chromium: 70.0.3538.35 (Official Build) beta(64-bit)
Revision	28dcb499844fa40c28d5f62e337876cb936f79f5-refs/branch-heads/3538@{#678}
OS	Mac OS X

• Verified when PDFJS is not installed, unable to view PDFs (prompted for download)
• Verified blacklist Chromium PDF Viewer #1386 (comment) also

Verification Passed on

Brave	0.55.11 Chromium: 70.0.3538.35 (Official Build) beta (64-bit)
Revision	28dcb499844fa40c28d5f62e337876cb936f79f5-refs/branch-heads/3538@{#678}
OS	Linux

Verification passed on

Brave	0.55.11 Chromium: 70.0.3538.35 (Official Build) beta (64-bit)
Revision	28dcb499844fa40c28d5f62e337876cb936f79f5-refs/branch-heads/3538@{#678}
OS	Windows 7