from internal bug 27577951:

"""
- Build Number (Home>Settings>About Phone> Build Number):  MHC19J
- Device: N5x

IMPORTANT : ATTACH BUG REPORT

STEPS TO REPRODUCE:
[Be as specific as possible; rather than "browse around a few web pages", say "go to this URL, then click on this specific link".]
1. Turn on TalkBack
2. Find a webview text box (I tested on YouTube search and email field creating a new Google account under settings)
3. Type something
4. Delete

EXPECTED RESULTS: TalkBack should read [key deleted] - for example, if you deleted "w" it should read "w deleted"

OBSERVED RESULTS: TalkBack reads only "Deleted"

NUMBER OF TIMES YOU WERE ABLE TO REPRODUCE(e.g. 3/10): 3/3

ADDITIONAL INFORMATION: Native text edits work fine, this issue is only on webviews.
"""

This is with Chrome 48.0.2564.95. The most reliable repro seems to be in Chrome on m.youtube.com, as in video attached on the internal bug.