Fix lifetime of leveldb::MojoEnv instances.

third_party/leveldatabase/env_chromium.cc

Index: third_party/leveldatabase/env_chromium.cc
diff --git a/third_party/leveldatabase/env_chromium.cc b/third_party/leveldatabase/env_chromium.cc
index b4daa541479b695c7b525c20973bc233a9d4da2c..337fdfc12c4d74aeef17e2899c0a049abda32305 100644
--- a/third_party/leveldatabase/env_chromium.cc
+++ b/third_party/leveldatabase/env_chromium.cc
@@ -559,9 +559,9 @@ ChromiumEnv::ChromiumEnv(const std::string& name)
 }
 
 ChromiumEnv::~ChromiumEnv() {
-  // In chromium, ChromiumEnv is leaked. It'd be nice to add NOTREACHED here to
-  // ensure that behavior isn't accidentally changed, but there's an instance in
-  // a unit test that is deleted.
+  // In chromium, ChromiumEnv is leaked. The NOTREACHED here is to ensure that
+  // behavior isn't accidentally changed.
+  NOTREACHED();
 }
 
 bool ChromiumEnv::FileExists(const std::string& fname) {