Add GC request to libFuzzers in attempt to avoid parasitic coverage.

test/fuzzer/fuzzer-support.cc

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "test/fuzzer/fuzzer-support.h"
 
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
 #include "include/libplatform/libplatform.h"
 
+#include "src/flags.h"
+
 namespace v8_fuzzer {
 
 namespace {
 
 FuzzerSupport* g_fuzzer_support = nullptr;
 
 void DeleteFuzzerSupport() {
   if (g_fuzzer_support) {
     delete g_fuzzer_support;
     g_fuzzer_support = nullptr;
   }
 }
 
 }  // namespace
 
 class FuzzerSupport::ArrayBufferAllocator : public v8::ArrayBuffer::Allocator {
  public:
   virtual void* Allocate(size_t length) {
     void* data = AllocateUninitialized(length);
     return data == NULL ? data : memset(data, 0, length);
   }
   virtual void* AllocateUninitialized(size_t length) { return malloc(length); }
   virtual void Free(void* data, size_t) { free(data); }
 };
 
 FuzzerSupport::FuzzerSupport(int* argc, char*** argv) {
+  v8::internal::FLAG_expose_gc = true;
   v8::V8::SetFlagsFromCommandLine(argc, *argv, true);
   v8::V8::InitializeICU();
   v8::V8::InitializeExternalStartupData((*argv)[0]);
   platform_ = v8::platform::CreateDefaultPlatform();
   v8::V8::InitializePlatform(platform_);
   v8::V8::Initialize();
 
   allocator_ = new ArrayBufferAllocator;
   v8::Isolate::CreateParams create_params;
   create_params.array_buffer_allocator = allocator_;
@@ skipping 42 matching lines @@
   return handle_scope.Escape(context);
 }
 
 }  // namespace v8_fuzzer
 
 extern "C" int LLVMFuzzerInitialize(int* argc, char*** argv) {
   v8_fuzzer::g_fuzzer_support = new v8_fuzzer::FuzzerSupport(argc, argv);
   atexit(&v8_fuzzer::DeleteFuzzerSupport);
   return 0;
 }