Use texture barriers to read directly from the RT

tests/GLProgramsTest.cpp

Index: tests/GLProgramsTest.cpp
diff --git a/tests/GLProgramsTest.cpp b/tests/GLProgramsTest.cpp
index 1f98b7ca4421260db1a48ddd63cbe3426eb1241a..d2cde88506be76e418e45fb2b4caff8e79f4b344 100644
--- a/tests/GLProgramsTest.cpp
+++ b/tests/GLProgramsTest.cpp
@@ -303,6 +303,12 @@ bool GrDrawTarget::programUnitTest(int maxStages) {
         if (pipeline.mustSkip()) {
             continue;
         }
+
+        GrXferBarrierType barrierType;
+        if (pipeline.getXferProcessor()->willNeedXferBarrier(rt, *gpu->caps(), &barrierType)) {
+            gpu->setXferBarrier(barrierType);
+        }
+
         GrBatchTracker bt;
         primProc->initBatchTracker(&bt, pipeline.getInitBatchTracker());