Disable zeroblock forcing for lossless coding mode

This to make sure that prediction residue always get coded in lossless
mode.

This commit also fixed lossless unit test

Change-Id: I537726ee55328d4e4cf0a0196393a67e12bfcde1

test/vp9_lossless_test.cc

diff --git a/test/vp9_lossless_test.cc b/test/vp9_lossless_test.cc
index 441cc44..30a3118 100644
--- a/test/vp9_lossless_test.cc
+++ b/test/vp9_lossless_test.cc
@@ -35,7 +35,7 @@
   }
 
   virtual void BeginPassHook(unsigned int /*pass*/) {
-    psnr_ = 0.0;
+    psnr_ = kMaxPsnr;
     nframes_ = 0;
   }
 
@@ -65,9 +65,9 @@
   init_flags_ = VPX_CODEC_USE_PSNR;
 
   // intentionally changed the dimension for better testing coverage
-  libvpx_test::I420VideoSource video("hantro_collage_w352h288.yuv", 356, 284,
+  libvpx_test::I420VideoSource video("hantro_collage_w352h288.yuv", 352, 288,
                                      timebase.den, timebase.num, 0, 30);
-
+  ASSERT_NO_FATAL_FAILURE(RunLoop(&video));
   const double psnr_lossless = GetMinPsnr();
   EXPECT_GE(psnr_lossless, kMaxPsnr);
 }

vp9/encoder/vp9_rdopt.c

diff --git a/vp9/encoder/vp9_rdopt.c b/vp9/encoder/vp9_rdopt.c
index 993919e..e49789e 100644
--- a/vp9/encoder/vp9_rdopt.c
+++ b/vp9/encoder/vp9_rdopt.c
@@ -609,7 +609,7 @@
 
   // TODO(jingning): temporarily enabled only for luma component
   rd = MIN(rd1, rd2);
-  if (plane == 0)
+  if (!xd->lossless && plane == 0)
     x->zcoeff_blk[tx_size][block] = rd1 > rd2 || !xd->plane[plane].eobs[block];
 
   args->this_rate += args->rate;