Dependencies are now added between the drawTargets in GrPipeline

src/gpu/GrRenderTarget.cpp

Index: src/gpu/GrRenderTarget.cpp
diff --git a/src/gpu/GrRenderTarget.cpp b/src/gpu/GrRenderTarget.cpp
index ad56cf761fff6e62afc5380d2532d9c82af48708..e547021227724d03e11ab0bb4c9053989eb8288e 100644
--- a/src/gpu/GrRenderTarget.cpp
+++ b/src/gpu/GrRenderTarget.cpp
@@ -16,6 +16,13 @@
 #include "GrRenderTargetPriv.h"
 #include "GrStencilAttachment.h"
 
+GrRenderTarget::~GrRenderTarget() {
+    if (fLastDrawTarget) {
+        fLastDrawTarget->clearRT();
+    }
+    SkSafeUnref(fLastDrawTarget);
+}
+
 void GrRenderTarget::discard() {
     // go through context so that all necessary flushing occurs
     GrContext* context = this->getContext();
@@ -57,24 +64,30 @@ void GrRenderTarget::overrideResolveRect(const SkIRect rect) {
 
 void GrRenderTarget::onRelease() {
     SkSafeSetNull(fStencilAttachment);
-    fLastDrawTarget = nullptr;
 
     INHERITED::onRelease();
 }
 
 void GrRenderTarget::onAbandon() {
     SkSafeSetNull(fStencilAttachment);
-    fLastDrawTarget = nullptr;
+
+    // The contents of this renderTarget are gone/invalid. It isn't useful to point back
+    // the creating drawTarget.
+    this->setLastDrawTarget(nullptr);
 
     INHERITED::onAbandon();
 }
 
 void GrRenderTarget::setLastDrawTarget(GrDrawTarget* dt) {
     if (fLastDrawTarget) {
+        // The non-MDB world never closes so we can't check this condition
+#ifdef ENABLE_MDB
         SkASSERT(fLastDrawTarget->isClosed());
+#endif
+        fLastDrawTarget->clearRT();
     }
 
-    fLastDrawTarget = dt;
+    SkRefCnt_SafeAssign(fLastDrawTarget, dt);
 }
 
 ///////////////////////////////////////////////////////////////////////////////