Utilities for content:// Uris and file modes.

Bug: 111268862, 111960973
Test: atest cts/tests/tests/content/src/android/content/cts/ContentUrisTest.java
Test: atest frameworks/base/core/tests/coretests/src/android/os/FileUtilsTest.java
Change-Id: I94373055468d279e6553d4a038267732b9b53745