Fix Linux compilation errors

[garrettr]

Fixes Linux compilation errors that were introduced in #77.

Submitter Checklist:

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Ran git rebase -i to squash commits (if needed).
• Tagged reviewers and labelled the pull request as needed.
• Request a security/privacy review as needed.

Test Plan:

1. Checkout this branch and run yarn run sync --run_hooks to apply the updated patches.
2. Build on Linux. The build should complete without errors.

Reviewer Checklist:

• New files have MPL-2.0 license header.
• Request a security/privacy review as needed.
• Adequate test coverage exists to prevent regressions

[garrettr]

These changes fix the build in my Ubuntu 16.04 VM. I ran into a confusing compilation error caused by sccache while working on this, but am going to file a separate issue for that since use of sccache is optional.

@AlexeyBarabash Could you confirm that this PR fixes your Linux builds?

[simonhong]

With this PR, I can build and run brave on linux(ubuntu 16.04).

[AlexeyBarabash]

++

[AlexeyBarabash]

Changes looks good. Build on Linux had succeeded. Thanks @garrettr .