Added support for Back/forward gesture with three finger swipe

[cndouglas]

Old title: Back/forward gesture should support three finger swipe

Test plan

#7786 (comment)

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• Did you search for similar issues before submitting this one?
  Yes.

• Describe the issue you encountered:
  As of 0.14.0, Brave supports a two finger swipe or none at all, depending on the user's system preferences. It should also support the three finger swipe if enabled in preferences.

• Platform (Win7, 8, 10? macOS? Linux distro?):
  macOS

• Brave Version (revision SHA):
  master (9ef7817)

• Steps to reproduce:

  1. Open System Preferences > Trackpad/Mouse > More Gestures.
  2. Change Swipe between pages to Swipe with three fingers.
  3. Open a new Brave tab and navigate to any site.
  4. Try to swipe backward with three fingers.

• Actual result:
  Nothing happens.

• Expected result:
  The browser should navigate back.

• Will the steps above reproduce in a fresh profile? If not what other info can be added?
  Yes.

• Is this an issue in the currently released version?
  Yes, 0.13.5 has the same issue.

• Can this issue be consistently reproduced?
  Yes.

• Extra QA steps:

  1. Open System Preferences > Trackpad/Mouse > More Gestures.
  2. Change Swipe between pages to Swipe with three fingers.
  3. Open a new Brave tab and navigate to any site.
  4. Try to swipe backward with three fingers.
  5. Make sure the page navigates back.

• Screenshot if needed:
  

• Any related issues:
  This is a follow-up to issue Fixed back/forward gesture to match system preferences #3299.

[lucidNTR]

updated the PR. let me know if any more changes are needed.

[darkdh]

fixed by #7786 7786