Dependencies are now added between the drawTargets in GrPipeline

src/gpu/GrDrawTarget.h

Index: src/gpu/GrDrawTarget.h
diff --git a/src/gpu/GrDrawTarget.h b/src/gpu/GrDrawTarget.h
index a487785a8b0c9650dd63eadd2e76d25b80ef98bb..d77615e6555faedcf6769b187cafa92f7da3cefa 100644
--- a/src/gpu/GrDrawTarget.h
+++ b/src/gpu/GrDrawTarget.h
@@ -33,6 +33,8 @@
 #include "SkTypes.h"
 #include "SkXfermode.h"
 
+//#define ENABLE_MDB 1
+
 class GrBatch;
 class GrBatchFlushState;
 class GrClip;
@@ -49,7 +51,7 @@ public:
 
     // The context may not be fully constructed and should not be used during GrDrawTarget
     // construction.
-    GrDrawTarget(GrGpu* gpu, GrResourceProvider*, const Options& options);
+    GrDrawTarget(GrRenderTarget* rt, GrGpu* gpu, GrResourceProvider*, const Options& options);
 
     ~GrDrawTarget() override;
 
@@ -62,6 +64,10 @@ public:
     }
     bool isClosed() const { return this->isSetFlag(kClosed_Flag); }
 
+    // TODO: this entry point is only needed in the non-MDB world. Remove when
+    // we make the switch to MDB
+    void clearRT() { fRenderTarget = nullptr; }
+
     /*
      * Notify this drawTarget that it relies on the contents of 'dependedOn'
      */
@@ -318,6 +324,7 @@ private:
 
     // 'this' drawTarget relies on the output of the drawTargets in 'fDependencies'
     SkTDArray<GrDrawTarget*>                    fDependencies;
+    GrRenderTarget*                             fRenderTarget;
 
     typedef SkRefCnt INHERITED;
 };