Fix browser test coverage, run in content-shell

[evanweible-wf]

Issue

• It's better to run coverage for browser tests using content-shell
  • Can pipe console logs to stdout
  • Easier integration with Travis CI
• Browser test run currently doesn't wait properly for tests to finish, resulting in incomplete and inconsistent coverage reporting when running large sets of tests

Changes

Source:

• Switch from Dartium to content-shell
• Listen to the test output from content-shell to determine when the tests are finished

Tests:

• Browser tests added to verify the browser use case

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@stevepeak @johnryan-wf

[evanweible-wf]

@trentgrover-wf @maxwellpeterson-wf

[maxwellpeterson-wf]

+1

[stevepeak]

There is the Codecov Bash uploader if that helps. I do prefer it being the uploader for consistency purposes. https://github.com/codecov/codecov-bash

[evanweible-wf]

@stevepeak I wasn't aware of that tool, thanks for pointing that out!

[johnryan-wf]

+1