Standardize source list variable naming in chrome_browser.gypi

Some variables use ...qualifier_feature_sources as names, other
use ...feature_qualifier_sources. This standardizes on the latter,
so that they can be grouped without breaking the flow of
the alphabetization that will be introduced in future CLs.

BUG=439765

Review URL: https://codereview.chromium.org/784673003

Cr-Commit-Position: refs/heads/master@{#307245}
2 files changed