base: Avoid calling VirtualAlloc with 0 length.

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 <stdint.h>
 
 #include "base/memory/discardable_shared_memory.h"
 #include "base/process/process_metrics.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ skipping 340 matching lines @@
   ASSERT_TRUE(rv);
 
   EXPECT_LE(0u, memory.mapped_size());
 
   // Memory is initially locked. Unlock it.
   memory.SetNow(Time::FromDoubleT(1));
   memory.Unlock(0, 0);
 
   // Lock and unlock memory.
   DiscardableSharedMemory::LockResult lock_rv = memory.Lock(0, 0);
-  EXPECT_EQ(DiscardableSharedMemory::SUCCESS, lock_rv);
+  EXPECT_NE(DiscardableSharedMemory::FAILED, lock_rv);
   memory.SetNow(Time::FromDoubleT(2));
   memory.Unlock(0, 0);
 }
 
 // This test checks that zero-filled pages are returned after purging a segment
 // when DISCARDABLE_SHARED_MEMORY_ZERO_FILL_ON_DEMAND_PAGES_AFTER_PURGE is
 // defined and MADV_REMOVE is supported.
 #if defined(DISCARDABLE_SHARED_MEMORY_ZERO_FILL_ON_DEMAND_PAGES_AFTER_PURGE)
 TEST(DiscardableSharedMemoryTest, ZeroFilledPagesAfterPurge) {
   const uint32_t kDataSize = 1024;
@@ skipping 27 matching lines @@
 
   // Check that reading memory after it has been purged is returning
   // zero-filled pages.
   uint8_t expected_data[kDataSize] = {};
   EXPECT_EQ(memcmp(memory2.memory(), expected_data, kDataSize), 0);
 }
 #endif
 
 }  // namespace
 }  // namespace base