Create a platform-dependent object for accessing purgeable memory.

src/ports/SkPurgeableMemoryBlock_none.cpp

+/*
+ * 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"
+
+bool SkPurgeableMemoryBlock::IsSupported() {
+    return false;
+}
+
+#ifdef SK_DEBUG
+bool SkPurgeableMemoryBlock::PlatformSupportsPurgingAllUnpinnedBlocks() {
+    return false;
+}
+
+bool SkPurgeableMemoryBlock::PurgeAllUnpinnedBlocks() {
+    return false;
+}
+
+bool SkPurgeableMemoryBlock::purge() {
+    return false;
+}
+#endif
+
+SkPurgeableMemoryBlock::SkPurgeableMemoryBlock(size_t size) {
+    SkASSERT(false);
+}
+
+SkPurgeableMemoryBlock::~SkPurgeableMemoryBlock() {
+}
+
+void* SkPurgeableMemoryBlock::pin(SkPurgeableMemoryBlock::PinResult*) {
+    return NULL;
+}
+
+void SkPurgeableMemoryBlock::unpin() {
+}
+