Create a platform-dependent object for accessing purgeable memory.

src/lazy/SkPurgeableMemoryBlock_common.cpp

Index: src/lazy/SkPurgeableMemoryBlock_common.cpp
diff --git a/src/lazy/SkPurgeableMemoryBlock_common.cpp b/src/lazy/SkPurgeableMemoryBlock_common.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..c1407321eff19b7689030fb52844d17ade839612
--- /dev/null
+++ b/src/lazy/SkPurgeableMemoryBlock_common.cpp
@@ -0,0 +1,17 @@
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkPurgeableMemoryBlock.h"
+
+SkPurgeableMemoryBlock* SkPurgeableMemoryBlock::CreatePurgeableMemoryBlock(size_t size) {
+    SkASSERT(PlatformSupportsPurgeableMemory());
+    if (!PlatformSupportsPurgeableMemory()) {
+        return NULL;
+    }
+    return SkNEW_ARGS(SkPurgeableMemoryBlock, (size));
+}
+