Enable leveldb build in GN world.

third_party/leveldatabase/env_chromium_unittest.cc

Index: third_party/leveldatabase/env_chromium_unittest.cc
diff --git a/third_party/leveldatabase/env_chromium_unittest.cc b/third_party/leveldatabase/env_chromium_unittest.cc
index fef1498572ed33619a0c75da11a4ed12370f6ec5..a72620a09e02bda533b2352219106079101607e2 100644
--- a/third_party/leveldatabase/env_chromium_unittest.cc
+++ b/third_party/leveldatabase/env_chromium_unittest.cc
@@ -246,12 +246,12 @@ TEST(ChromiumEnv, GetChildrenPriorResults) {
   std::vector<std::string> result;
   leveldb::Status status = env->GetChildren(dir.AsUTF8Unsafe(), &result);
   EXPECT_TRUE(status.ok());
-  EXPECT_EQ(1, result.size());
+  EXPECT_EQ(1U, result.size());
 
   // And a second time should also return one result
   status = env->GetChildren(dir.AsUTF8Unsafe(), &result);
   EXPECT_TRUE(status.ok());
-  EXPECT_EQ(1, result.size());
+  EXPECT_EQ(1U, result.size());
 }
 
 int main(int argc, char** argv) { return base::TestSuite(argc, argv).Run(); }