Large blank block on screen when use less

• iTerm2 version: 3.0.0
• OS version: 10.10.4

Detailed steps to reproduce the problem:

1. Execute ls or something else, make sure your cursor is locate at the middle part of the screen.
2. Execute command less, like less somefile, but the file's content should not full fill the screen.

What happened: There are large blank block between the cursor to the top.

What should have happened: In the old version of iTerm2, the file content start from the top of the screen.

Dup of #3408 (closed)

Status changed to closed