Add a standard placement new operator to WTF_USE_ALLOCATOR.

third_party/WebKit/Source/wtf/VectorTest.cpp

Index: third_party/WebKit/Source/wtf/VectorTest.cpp
diff --git a/third_party/WebKit/Source/wtf/VectorTest.cpp b/third_party/WebKit/Source/wtf/VectorTest.cpp
index 74b08ca5bdc19e93e4113672f360496a65966b2a..aa7509b11586e4ed79b13f43e3ca1f5165a11aa1 100644
--- a/third_party/WebKit/Source/wtf/VectorTest.cpp
+++ b/third_party/WebKit/Source/wtf/VectorTest.cpp
@@ -27,6 +27,7 @@
 
 #include "testing/gtest/include/gtest/gtest.h"
 #include "wtf/HashSet.h"
+#include "wtf/Optional.h"
 #include "wtf/PtrUtil.h"
 #include "wtf/text/WTFString.h"
 #include <memory>
@@ -688,6 +689,15 @@ TEST(VectorTest, InitializerList)
     EXPECT_EQ(3, vector3[2]);
 }
 
+TEST(VectorTest, Optional)
+{
+    Optional<Vector<int>> vector;
+    EXPECT_FALSE(vector);
+    vector.emplace(3);
+    EXPECT_TRUE(vector);
+    EXPECT_EQ(3u, vector->size());
+}
+
 static_assert(VectorTraits<int>::canCopyWithMemcpy, "int should be copied with memcopy.");
 static_assert(VectorTraits<char>::canCopyWithMemcpy, "char should be copied with memcpy.");
 static_assert(VectorTraits<LChar>::canCopyWithMemcpy, "LChar should be copied with memcpy.");