Correctly handle strings styled with HTML markup

Only a small subset of HTML is supported for styling strings. This
replicates exactly what the Android framework by copying how StringBlock
handles HTML markup.

Bug: 184782424
Test: Test added in ResourceHelper.java
Change-Id: Ic57f18a34b6d5fbb4aa9456e71ac0ae6b1d63c96
(cherry picked from commit b477949b988b42b5b7c57e3b8d092f541763028a)
4 files changed