Re-land: base: Implement browser process support for discardable memory.

base/test/test_discardable_memory_shmem_allocator.cc

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/test/test_discardable_memory_shmem_allocator.h"
+
+#include <stdint.h>
+
+namespace base {
+namespace {
+
+class DiscardableMemoryShmemChunkImpl : public DiscardableMemoryShmemChunk {
+ public:
+  explicit DiscardableMemoryShmemChunkImpl(size_t size)
+      : memory_(new uint8_t[size]) {}
+
+  // Overridden from DiscardableMemoryShmemChunk:
+  bool Lock() override { return false; }

[danakj, 2015/03/13 21:59:07]

lock returning false i found surprising, then things won't use this memory?

[reveman, 2015/03/13 22:07:33]

The memory is locked initially. It will always fail the second time the client
tries to use the memory and have to call Lock(). This is useful for testing
purposes as it makes sure code that is using discardable memory is handling the
case when memory has been purged properly.

[danakj, 2015/03/13 22:32:45]

OK.

+  void Unlock() override {}
+  void* Memory() const override { return memory_.get(); }
+
+ private:
+  scoped_ptr<uint8_t[]> memory_;
+};
+
+}  // namespace
+
+TestDiscardableMemoryShmemAllocator::TestDiscardableMemoryShmemAllocator() {
+}
+
+TestDiscardableMemoryShmemAllocator::~TestDiscardableMemoryShmemAllocator() {
+}
+
+scoped_ptr<DiscardableMemoryShmemChunk>
+TestDiscardableMemoryShmemAllocator::AllocateLockedDiscardableMemory(
+    size_t size) {
+  return make_scoped_ptr(new DiscardableMemoryShmemChunkImpl(size));
+}
+
+}  // namespace base