Add GrProgramElement base class for GrEffect with deferred exec ref.

include/gpu/GrProgramResource.h

+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef GrProgramResource_DEFINED
+#define GrProgramResource_DEFINED
+
+#include "SkRefCnt.h"
+
+class GrGpuResource;
+
+/**
+ * Class that wraps a resource referenced by a GrProgramElement or GrDrawState. It manages
+ * converting refs to pending io operations. Like SkAutoTUnref, its constructor and setter adopt
+ * a ref from their caller. This class is intended only for internal use in core Gr code.
+ */
+class GrProgramResource : SkNoncopyable {
+public:
+    enum IOType {
+        kRead_IOType,
+        kWrite_IOType,
+        kRW_IOType,
+
+        kNone_IOType, // For internal use only, don't specify to constructor or setResource().
+    };
+
+    SK_DECLARE_INST_COUNT_ROOT(GrProgramResource);
+    GrProgramResource();
+
+    /** Adopts a ref from the caller. ioType expresses what type of IO operations will be marked as
+        pending on the resource when markPendingIO is called. */
+    explicit GrProgramResource(GrGpuResource*, IOType ioType);
+
+    ~GrProgramResource();
+
+    GrGpuResource* getResource() const { return fResource; }
+
+    /** Adopts a ref from the caller. ioType expresses what type of IO operations will be marked as
+        pending on the resource when markPendingIO is called. */
+    void setResource(GrGpuResource*, IOType ioType);
+
+    /** Does this object own a pending read or write on the resource it is wrapping. */
+    bool ownsPendingIO() const { return fPendingIO; }
+
+    /** Shortcut for calling setResource() with NULL. It cannot be called after markingPendingIO
+        is called. */
+    void reset();
+
+private:
+    /** Called by owning GrProgramElement when the program element is first scheduled for
+        execution. */
+    void markPendingIO() const;
+
+    /** Called when the program element/draw state is no longer owned by GrDrawTarget-client code.
+        This lets the cache know that the drawing code will no longer schedule additional reads or
+        writes to the resource using the program element or draw state. */
+    void removeRef() const;
+
+    friend class GrDrawState;
+    friend class GrProgramElement;
+
+    GrGpuResource*      fResource;
+    mutable bool        fOwnRef;
+    mutable bool        fPendingIO;
+    IOType              fIOType;
+
+    typedef SkNoncopyable INHERITED;
+};
+
+#endif