GLProgramsTest can now randomly create a tree of GrFragmentProcessors instead of a linear pipeline

include/core/SkComposeShader.h

Index: include/core/SkComposeShader.h
diff --git a/include/core/SkComposeShader.h b/include/core/SkComposeShader.h
index 956ba6e00d2ad003ae27817160bb359003d3d5c0..763a1daa45e21a8c624c48c511bf7525fd1406a8 100644
--- a/include/core/SkComposeShader.h
+++ b/include/core/SkComposeShader.h
@@ -84,4 +84,46 @@ private:
     typedef SkShader INHERITED;
 };
 
+#if SK_SUPPORT_GPU
+
+#include "SkString.h"
+#include "../gpu/GrFragmentProcessor.h"
+
+/////////////////////////////////////////////////////////////////////
+
+class GrComposeEffect : public GrFragmentProcessor {
+public:
+
+    static GrFragmentProcessor* Create(const GrFragmentProcessor* fpA,
+                                       const GrFragmentProcessor* fpB,
+                                       SkXfermode::Mode mode);
+    const char* name() const override {return fName.c_str(); }
+    void onGetGLProcessorKey(const GrGLSLCaps& caps, GrProcessorKeyBuilder* b) const override;
+
+    SkXfermode::Mode getMode() const { return fMode; }
+    int getShaderAChildIndex() const { return fShaderAChildIndex; }
+    int getShaderBChildIndex() const { return fShaderBChildIndex; }
+
+protected:
+    bool onIsEqual(const GrFragmentProcessor&) const override;
+    void onComputeInvariantOutput(GrInvariantOutput* inout) const override;
+
+private:
+    GrComposeEffect(const GrFragmentProcessor* fpA, const GrFragmentProcessor* fpB,
+                    SkXfermode::Mode mode);
+
+    GrGLFragmentProcessor* onCreateGLInstance() const override;
+
+    SkString fName;
+    int fShaderAChildIndex;
+    int fShaderBChildIndex;
+    SkXfermode::Mode fMode;
+
+    GR_DECLARE_FRAGMENT_PROCESSOR_TEST;
+
+    typedef GrFragmentProcessor INHERITED;
+};
+
+#endif
+
 #endif