Re-land: base: Replace PurgeAndTruncate with Shrink function.

base/memory/discardable_shared_memory_unittest.cc

 // Copyright 2014 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/basictypes.h"
 #include "base/memory/discardable_shared_memory.h"
 #include "base/process/process_metrics.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
@@ skipping 293 matching lines @@
   bool rv = memory.CreateAndMap(kDataSize);
   ASSERT_TRUE(rv);
 
   EXPECT_LE(kDataSize, memory.mapped_size());
 
   // Mapped size should be 0 after memory segment has been closed.
   memory.Close();
   EXPECT_EQ(0u, memory.mapped_size());
 }
 
+TEST(DiscardableSharedMemoryTest, Shrink) {
+  if (!DiscardableSharedMemory::IsShrinkingSupported())

[danakj, 2015/03/18 23:18:52]

Do you think you could add platform #ifs here instead of early out based on
production code? Maybe you can verify this IsShrinkingSupported thing does what
you want too, to make people notice this test if they change that function?

[reveman, 2015/03/19 02:21:54]

I removed IsShrinkingSupported from latest patch and added #ifs around Shrink()
instead. That keeps things simple and I think it's more consistent with other
classes in base/ such as SharedMemory. PTAL.

+    return;
+
+  const uint32 kDataSize = 1024;
+
+  TestDiscardableSharedMemory memory;
+  bool rv = memory.CreateAndMap(kDataSize);
+  ASSERT_TRUE(rv);
+
+  EXPECT_NE(0u, memory.mapped_size());
+
+  // Mapped size should be 0 after shrinking memory segment.
+  memory.Shrink();
+  EXPECT_EQ(0u, memory.mapped_size());
+}
+
 }  // namespace
 }  // namespace base