Revert of base: Fix DiscardableSharedMemory::mapped_size().

base/memory/discardable_shared_memory_unittest.cc

Index: base/memory/discardable_shared_memory_unittest.cc
diff --git a/base/memory/discardable_shared_memory_unittest.cc b/base/memory/discardable_shared_memory_unittest.cc
index 896263df60927b6df3aaba8a3628f5ea5a203f81..90441e1f35f47f8ab4db8eb79d5fe8998bf5e12f 100644
--- a/base/memory/discardable_shared_memory_unittest.cc
+++ b/base/memory/discardable_shared_memory_unittest.cc
@@ -287,19 +287,5 @@
   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