Word spacing in RTL for segments

Removed m_stop and length comparison as they carry different units i.e. if there are two char text then m_stop will be 1 and length 2. As do not compare, needWordSpace does not set correct value.  

Also by default condition for needSpacing has been changed to true because if first character is space it was getting omitted. 

BUG=344873
R=leviw, eae
TEST=Word spacing in RTL with different segments handling.

Review URL: https://codereview.chromium.org/343443002

git-svn-id: svn://svn.chromium.org/blink/trunk@176416 bbb929c8-8fbe-4397-9dbb-9b2b20218538