[jumbo] add test source file namespace in test-hashmap.cc

Bug: chromium:746958
Change-Id: Ia251d99ffe142fadb99fc83082683aa87676c47d
Reviewed-on: https://chromium-review.googlesource.com/680574
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Mostyn Bramley-Moore <mostynb@opera.com>
Cr-Commit-Position: refs/heads/master@{#48145}

test/cctest/test-hashmap.cc

@@ -34,6 +34,7 @@
 
 namespace v8 {
 namespace internal {
+namespace test_hashmap {
 
 typedef uint32_t (*IntKeyHash)(uint32_t key);
 
@@ -173,5 +174,6 @@ TEST(HashSet) {
   TestSet(CollisionHash, 50);
 }
 
+}  // namespace test_hashmap
 }  // namespace internal
 }  // namespace v8