Update from https://crrev.com/316786

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 216 matching lines @@
 
   memory2.SetNow(Time::FromDoubleT(1));
   memory2.Unlock(0, 0);
 
   rv = memory2.Purge(Time::FromDoubleT(2));
   EXPECT_TRUE(rv);
 
   // Lock should fail as memory has been purged.
   auto lock_rv = memory2.Lock(0, 0);
   EXPECT_EQ(DiscardableSharedMemory::FAILED, lock_rv);
-  lock_rv = memory1.Lock(0, 0);
-  EXPECT_EQ(DiscardableSharedMemory::FAILED, lock_rv);
 }
 
 TEST(DiscardableSharedMemoryTest, LockAndUnlockRange) {
   const uint32 kDataSize = 32;
 
   uint32 data_size_in_bytes = kDataSize * base::GetPageSize();
 
   TestDiscardableSharedMemory memory1;
   bool rv = memory1.CreateAndMap(data_size_in_bytes);
   ASSERT_TRUE(rv);
 
   SharedMemoryHandle shared_handle;
   ASSERT_TRUE(
       memory1.ShareToProcess(GetCurrentProcessHandle(), &shared_handle));
   ASSERT_TRUE(SharedMemory::IsHandleValid(shared_handle));
 
   TestDiscardableSharedMemory memory2(shared_handle);
   rv = memory2.Map(data_size_in_bytes);
   ASSERT_TRUE(rv);
 
   // Unlock first page.
   memory2.SetNow(Time::FromDoubleT(1));
   memory2.Unlock(0, base::GetPageSize());
 
   rv = memory1.Purge(Time::FromDoubleT(2));
   EXPECT_FALSE(rv);
 
+  // Lock first page again.
+  memory2.SetNow(Time::FromDoubleT(3));
+  auto lock_rv = memory2.Lock(0, base::GetPageSize());
+  EXPECT_NE(DiscardableSharedMemory::FAILED, lock_rv);
+
+  // Unlock first page.
+  memory2.SetNow(Time::FromDoubleT(4));
+  memory2.Unlock(0, base::GetPageSize());
+
+  rv = memory1.Purge(Time::FromDoubleT(5));
+  EXPECT_FALSE(rv);
+
   // Unlock second page.
-  memory2.SetNow(Time::FromDoubleT(3));
+  memory2.SetNow(Time::FromDoubleT(6));
   memory2.Unlock(base::GetPageSize(), base::GetPageSize());
 
-  rv = memory1.Purge(Time::FromDoubleT(4));
+  rv = memory1.Purge(Time::FromDoubleT(7));
   EXPECT_FALSE(rv);
 
   // Unlock anything onwards.
-  memory2.SetNow(Time::FromDoubleT(5));
+  memory2.SetNow(Time::FromDoubleT(8));
   memory2.Unlock(2 * base::GetPageSize(), 0);
 
   // Memory is unlocked, but our usage timestamp is incorrect.
-  rv = memory1.Purge(Time::FromDoubleT(6));
+  rv = memory1.Purge(Time::FromDoubleT(9));
   EXPECT_FALSE(rv);
 
   // The failed purge attempt should have updated usage time to the correct
   // value.
-  EXPECT_EQ(Time::FromDoubleT(5), memory1.last_known_usage());
+  EXPECT_EQ(Time::FromDoubleT(8), memory1.last_known_usage());
 
   // Purge should now succeed.
-  rv = memory1.Purge(Time::FromDoubleT(7));
+  rv = memory1.Purge(Time::FromDoubleT(10));
   EXPECT_TRUE(rv);
 }
 
 TEST(DiscardableSharedMemoryTest, MappedSize) {
   const uint32 kDataSize = 1024;
 
   TestDiscardableSharedMemory memory;
   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());
 }
 
 }  // namespace
 }  // namespace base