Prevent clang from optimizing away a variable.

base/tools_sanity_unittest.cc

Index: base/tools_sanity_unittest.cc
diff --git a/base/tools_sanity_unittest.cc b/base/tools_sanity_unittest.cc
index 249ec71946a568bc3f20f289c4135008d1b7ca11..ec7b1cc93949f889d1d92348782fb5d1c788ff4a 100644
--- a/base/tools_sanity_unittest.cc
+++ b/base/tools_sanity_unittest.cc
@@ -74,7 +74,8 @@ void MakeSomeErrors(char *ptr, size_t size) {
 
 // A memory leak detector should report an error in this test.
 TEST(ToolsSanityTest, MemoryLeak) {
-  int *leak = new int[256];  // Leak some memory intentionally.
+  // Without the |volatile|, clang optimizes away the next two lines.
+  int* volatile leak = new int[256];  // Leak some memory intentionally.
   leak[4] = 1;  // Make sure the allocated memory is used.
 }