Fix a FORWARD_NULL defect reported by Coverity.

Fix a FORWARD_NULL defect reported by Coverity. 

We never construct a ScrollView object with a null horiz_sb_ 
or vert_sb_ member, and we already dereference horiz_sb_ and 
vert_sb_ without null checking in many places (including the 
destructor), so all the null checks for horiz_sb_ and vert_sb_ 
are unnecessary. 

Original review URL: http://codereview.chromium.org/155980/

R=ben@chromium.org
BUG=17101
TEST=none

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=113350

[Ben Goodger (Google), 2011-12-06 22:12:28]

lgtm

[commit-bot: I haz the power, 2011-12-07 03:06:16]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/wtc@chromium.org/8827007/1

[commit-bot: I haz the power, 2011-12-07 05:04:22]

Change committed as 113350