Change empty_fuzzer to reflect good patterns

Don't create Environment outside of LLVMFuzzerTestOneInput.

TBR=mmoroz@chromium.org

Change-Id: I470016153ec30ed09805ef8dce8baa2b8103d8d1
Reviewed-on: https://chromium-review.googlesource.com/c/1318401
Commit-Queue: Jonathan Metzman <metzman@chromium.org>
Reviewed-by: Max Moroz <mmoroz@chromium.org>
Reviewed-by: Jonathan Metzman <metzman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605413}

testing/libfuzzer/fuzzers/empty_fuzzer.cc

@@ -7,12 +7,6 @@
 #include <stddef.h>
 #include <stdint.h>
 
-// Fuzzer entry point.
-extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
-  // Run your code on data.
-  return 0;
-}
-
 // Environment is optional.
 struct Environment {
   Environment() {
@@ -20,6 +14,10 @@ struct Environment {
   }
 };
 
-Environment* env = new Environment();
-
-
+// Fuzzer entry point.
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
+  // Initialize environment once.
+  static Environment env;
+  // Run your code on data.
+  return 0;
+}