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 ed74ae8f6a65ae828a3c0727580ae1622d6b03db..256c577badc31a252dea7f9fef84c4af9d34efe4 100644
--- a/tests/GLProgramsTest.cpp
+++ b/tests/GLProgramsTest.cpp
@@ -316,6 +316,12 @@ 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());