Expected

I expect a double space to insert a period at the end of the previous word. abc.

Observed

A double space inserts a space+period after the last word. abc .

Reproduced

1. Type a word in the content area
2. Tap a space twice rapidly
3. You will see a space+period at the end of the last typed word.

Tested

Moto G (3rd Gen) on Android 6.0 with alpha-35