From bsazonov's initial investigation:

"""
It looks like there's already a lot of code for adding/removing dividers: https://cs.chromium.org/chromium/src/chrome/android/java/src/org/chromium/chrome/browser/preferences/ChromeSwitchPreference.java?l=56, https://cs.chromium.org/chromium/src/chrome/android/java/src/org/chromium/chrome/browser/preferences/autofill/AndroidPaymentAppPreference.java?l=55, https://cs.chromium.org/chromium/src/chrome/android/java/src/org/chromium/chrome/browser/preferences/SearchEnginePreference.java?l=55, and more.

We could solve all these divider problems once and forever would be using android.support.v7.preference.Preference instead of android.preference.Preference.

Pros:
1. android.support.v7.preference.PreferenceViewHolder has setDividerAllowedAbove & setDividerAllowedBelow, that would allow easy dividers management.
2. Using android.support.v7.preference.SwitchPreferenceCompat would allow us to get rid of ChromeSwitchPreference.
3. No minor workarounds like this one: https://cs.chromium.org/chromium/src/chrome/android/java/src/org/chromium/chrome/browser/preferences/ChromeBaseListPreference.java?l=57.
4. Support library will (hopefully) provide more consistent appearance and behavior on different Android versions.
"""

One thing we'd need to verify is the APK size increase that would result from switching to app compat.  If it was a large increase, we might have to live with the current Preferences behavior.

Nearly all times that we have migrated to the support library (or updated the support library to major revs), we've run into compatibility and expectation issues between what Chrome and the support library expect.  While this could be a straightforward migration, it could also uncover oodles, and oodles of issues that we'd to address on multiple different Android platforms.