Move hypertext_ member to AXPlatformNodeBsae

These classes will soon share a good deal of code that reads this member
variable. This change eliminates the duplicate member that exists in the
subclasses

Bug: 866338
Change-Id: I2b4825f511c94754be618d1ddcaaffc20e8473c4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1524299
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: Martin Robinson <mrobinson@igalia.com>
Cr-Commit-Position: refs/heads/master@{#642047}
6 files changed