Allow gpu ResourceHandle class to be shared for multiple purposes

src/gpu/GrResourceHandle.h

+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+*/
+
+#ifndef GrResourceHandle_DEFINED
+#define GrResourcehandle_DEFINED
+
+#include "SkTypes.h"
+
+// Opaque handle to a resource
+class GrResourceHandle {
+public:
+    GrResourceHandle(int value) : fValue(value) {
+        SkASSERT(this->isValid());
+    }
+
+    GrResourceHandle() : fValue(kInvalid_ResourceHandle) {}
+protected:
+    bool operator==(const GrResourceHandle& other) const { return other.fValue == fValue; }
+    bool isValid() const { return kInvalid_ResourceHandle != fValue; }
+    int toIndex() const { SkASSERT(this->isValid()); return fValue; }
+
+private:
+    static const int kInvalid_ResourceHandle = -1;
+    int fValue;
+};
+
+// Creates a resource handle class with the name, name, which exposes the protected functions of the
+// handle class to be used on the sub class
+#define GR_CREATE_RESOURCE_HANDLE_CLASS(name) \

[bsalomon, 2016/05/06 17:37:54]

What do you think about simplifying this by making GrResourceHandle templated on
a const char* and then doing


#define GR_CREATE_RESOURCE_HANDLE_CLASS(name)
static const char k##name_tag[] = #name
using name = GrResourceKey<k##name_tag>

Also, I might prefer DEFINE to CREATE... 

+    class name : public GrResourceHandle {    \
+    private:                                  \
+        typedef GrResourceHandle INHERITED;   \
+    public:                                   \
+        using INHERITED::INHERITED;           \
+        using INHERITED::operator==;          \
+        using INHERITED::isValid;             \
+        using INHERITED::toIndex;             \
+     }
+
+
+
+#endif