Create GrDraw and start fast pathing src over rects

src/gpu/draws/GrDraw.h

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef GrDraw_DEFINED
+#define GrDraw_DEFINED
+
+#include "GrNonAtomicRef.h"
+
+#include "GrRenderTarget.h"
+
+class GrDrawTarget;
+
+#define GRDRAW_ASSERT_OWNED_RESOURCE(R) SkASSERT(!(R) || (R)->getContext() == fContext)
+
+/*
+ * GrDraw is a base class which captures the scope of the entry point on SkGpuDevice where it
+ * originates.  The purpose of a GrDraw is to encapsulate a set of decisions about the type of
+ * GrBatch Ganesh will create for a given primitive.  It is also responsible for transforming the
+ * SkPaint.  A GrDraw should also leave some kind of GrDrawSnap on the GrBatch it creates, as a way
+ * for it to fastpath drawing decisions.  In the fastpath case, a GrDraw should batch draw calls
+ * without transforming the SkPaint, by directly pushing new geometry onto existing GrBatches
+ *
+ * A GrDraw must be able to fully draw itself if fastpath batching is not possible.
+ *
+ * The only reason this base class exists is so that all GrDraw's have separate class IDs
+ */
+
+class GrDraw {
+public:
+    // Each derived class must have a unique class id. This is achieved by providing each
+    // derived class with a templatized version of ClassID() which uses the GrDraw-global
+    // gCurrDrawClassID counter.
+    template <typename PROC_SUBCLASS> static uint32_t ClassID() {
+         static uint32_t kClassID = GenID(&gCurrDrawClassID);
+         return kClassID;
+    }
+
+protected:
+    static uint32_t GenID(int32_t* idCounter) {
+        // The atomic inc returns the old value not the incremented value. So we add
+        // 1 to the returned value.
+        uint32_t id = static_cast<uint32_t>(sk_atomic_inc(idCounter)) + 1;
+        if (!id) {
+            SkFAIL("This should never wrap as it should only be called once for each GrDraw "
+                   "subclass.");
+        }
+        return id;
+    }
+
+    enum {
+        kIllegalDrawClassID = 0
+    };
+
+    static int32_t gCurrDrawClassID;
+
+    friend class GrDrawSnap; // for class ID stuff
+};
+
+/*
+ * A GrDrawSnap is the marker a GrDraw can use to determine whether or not it can take a fastpath.
+ * After creation, a GrDrawSnap subclass will live directly on a GrBatch
+ */
+class GrDrawSnap : public GrNonAtomicRef {
+public:
+    GrDrawSnap() : fClassID(GrDraw::kIllegalDrawClassID) {}
+    uint32_t classID() const {
+        SkASSERT(fClassID != GrDraw::kIllegalDrawClassID);
+        return fClassID;
+    }
+
+protected:
+    uint32_t fClassID;
+    typedef GrNonAtomicRef INHERITED;
+};
+
+#endif