Compatibility method to check system settings write permission

SettingsCompat.System.canWrite returns true for versions older than M
because prior to M, permissions had to be granted prior to installing
the app. It's only in M and above that we check for permissions at
runtime.

Bug:25776171
Change-Id: Iee2250248223e7237f8eaa506b277e301e289cc0
4 files changed
tree: 4bf1a206afd293a9ee17970c29d18db6204fc76e
  1. res/
  2. src/
  3. tests/
  4. Android.mk
  5. AndroidManifest.xml
  6. proguard.flags