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

This implements support for in-process discardable
memory. Each in-process discardable memory instance is
associated with a discardable shared memory segment. This
is hopefully efficient enough with the limited use of
discardable memory in the browser process.
DiscardableSharedMemoryHeap can be used if this is not
enough.

This also moves the test implementation of the discardable
memory allocator into a TestDiscardableMemoryShmemAllocator
class and requires tests that use discardable memory to
explicitly use this test allocator. Browser tests uses the
real discardable memory allocator.

BUG=422953,463250

Review URL: https://codereview.chromium.org/1004043002

Cr-Commit-Position: refs/heads/master@{#320764}

3 files changed, 70 insertions, 0 deletions

diff --git a/base/test/BUILD.gn b/base/test/BUILD.gn
index 55e710d..f5d2e4c 100644
--- a/base/test/BUILD.gn
+++ b/base/test/BUILD.gn
@@ -81,6 +81,8 @@ source_set("test_support") {
     "simple_test_tick_clock.h",
     "task_runner_test_template.cc",
     "task_runner_test_template.h",
+    "test_discardable_memory_shmem_allocator.cc",
+    "test_discardable_memory_shmem_allocator.h",
     "test_file_util.cc",
     "test_file_util.h",
     "test_file_util_android.cc",
diff --git a/base/test/test_discardable_memory_shmem_allocator.cc b/base/test/test_discardable_memory_shmem_allocator.cc
new file mode 100644
index 0000000..24185a2
--- /dev/null
+++ b/base/test/test_discardable_memory_shmem_allocator.cc
@@ -0,0 +1,40 @@
+// 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; }
+  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
diff --git a/base/test/test_discardable_memory_shmem_allocator.h b/base/test/test_discardable_memory_shmem_allocator.h
new file mode 100644
index 0000000..a40960e
--- /dev/null
+++ b/base/test/test_discardable_memory_shmem_allocator.h
@@ -0,0 +1,28 @@
+// 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.
+
+#ifndef BASE_TEST_TEST_DISCARDABLE_MEMORY_SHMEM_ALLOCATOR_H_
+#define BASE_TEST_TEST_DISCARDABLE_MEMORY_SHMEM_ALLOCATOR_H_
+
+#include "base/memory/discardable_memory_shmem_allocator.h"
+
+namespace base {
+
+class TestDiscardableMemoryShmemAllocator
+    : public DiscardableMemoryShmemAllocator {
+ public:
+  TestDiscardableMemoryShmemAllocator();
+  ~TestDiscardableMemoryShmemAllocator() override;
+
+  // Overridden from DiscardableMemoryShmemAllocator:
+  scoped_ptr<DiscardableMemoryShmemChunk> AllocateLockedDiscardableMemory(
+      size_t size) override;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(TestDiscardableMemoryShmemAllocator);
+};
+
+}  // namespace base
+
+#endif  // BASE_TEST_TEST_DISCARDABLE_MEMORY_SHMEM_ALLOCATOR_H_