Revert of base: Replace PurgeAndTruncate with Shrink function.

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 ae7235d108cd69e2effdb732a41d0bd2d5e05457..74d19a64527187678a4109e01d85fa2b1b700e53 100644
--- a/base/memory/discardable_shared_memory_unittest.cc
+++ b/base/memory/discardable_shared_memory_unittest.cc
@@ -311,21 +311,5 @@
   EXPECT_EQ(0u, memory.mapped_size());
 }
 
-#if defined(DISCARDABLE_SHARED_MEMORY_SHRINKING)
-TEST(DiscardableSharedMemoryTest, Shrink) {
-  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());
-}
-#endif
-
 }  // namespace
 }  // namespace base