OSX App Launcher UI nit: cleaner lines for pager buttons.

Use floor() for the vertical position of the clip rectangle used for
pager buttons on the OSX app list for cleaner horizontal lines.

Without this, the lines are blurry because the buttons are vertically
centered and the height of the pager area is an odd number.

BUG=138633

Review URL: https://chromiumcodereview.appspot.com/17183014

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@207316 0039d316-1c4b-4281-b951-d872f2087c98

ui/app_list/cocoa/app_list_pager_view.mm

@@ -134,7 +134,7 @@ - (void)drawSegment:(NSInteger)segment
   gfx::ScopedNSGraphicsContextSaveGState context;
   NSRect clipRect = NSMakeRect(
       frame.origin.x + kButtonStripPadding / 2,
-      frame.origin.y + (frame.size.height - kButtonHeight) / 2,
+      floor(frame.origin.y + (frame.size.height - kButtonHeight) / 2),
       frame.size.width - kButtonStripPadding,
       kButtonHeight);
   [[NSBezierPath bezierPathWithRoundedRect:clipRect