add pipecanvas

include/private/SkRefSet.h

Index: include/private/SkRefSet.h
diff --git a/include/private/SkRefSet.h b/include/private/SkRefSet.h
new file mode 100644
index 0000000000000000000000000000000000000000..5f23ba2191b36afac855da95324436d1e0074a80
--- /dev/null
+++ b/include/private/SkRefSet.h
@@ -0,0 +1,40 @@
+/*
+ * 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 SkRefSet_DEFINED
+#define SkRefSet_DEFINED
+
+#include "SkRefCnt.h"
+#include "SkTDArray.h"
+
+template <typename T> class SkRefSet {
+public:
+    ~SkRefSet() { fArray.unrefAll(); }
+
+    T* get(int index) const {
+        SkASSERT((unsigned)index < (unsigned)fArray.count());
+        return fArray[index];
+    }
+
+    bool set(int index, T* value) {
+        if ((unsigned)index < (unsigned)fArray.count()) {
+            SkRefCnt_SafeAssign(fArray[index], value);
+            return true;
+        }
+        if (fArray.count() == index && value) {
+            *fArray.append() = SkRef(value);
+            return true;
+        }

[mtklein_C, 2016/09/12 19:47:58]

The particular invariants of this class (values must start non-null, but can be
later reset to null) seem SkPipeReader-specific.  I think you might want to move
this into SkPipeReader.cpp?

[reed1, 2016/09/12 21:35:22]

Done.

+        SkDebugf("SkRefSet: index [%d] out of range %d\n", index, fArray.count());
+        return false;
+    }
+
+private:
+    SkTDArray<T*> fArray;
+};
+
+#endif