Take the ceil() of the width and height of the new render target.

This was removed in ag/31004652 by mistake and might be causing the null pointer exception in 387410516.

Also re-enable setting blur algorithm to KAWASE for testing.

Bug: 387410516
Test: atest BlurTests
Flag: com.android.graphics.surfaceflinger.flags.window_blur_kawase2
Change-Id: I08e53b1eac4f649a76afc21881609fe6abd2337b