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

R=aizatsky@chromium.org, jochen@chromium.org, kcc@chromium.org, ochang@chromium.org
BUG=584819
LOG=Y

Review-Url: https://codereview.chromium.org/1927933002
Cr-Commit-Position: refs/heads/master@{#35866}

test/fuzzer/fuzzer-support.cc

@@ -10,6 +10,8 @@
 
 #include "include/libplatform/libplatform.h"
 
+#include "src/flags.h"
+
 namespace v8_fuzzer {
 
 namespace {
@@ -36,6 +38,7 @@ class FuzzerSupport::ArrayBufferAllocator : public v8::ArrayBuffer::Allocator {
 };
 
 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]);

test/fuzzer/json.cc

@@ -27,5 +27,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
   }
 
   v8::JSON::Parse(support->GetContext(), source).IsEmpty();
+  isolate->RequestGarbageCollectionForTesting(
+      v8::Isolate::kFullGarbageCollection);
   return 0;
 }

test/fuzzer/parser.cc

@@ -38,5 +38,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
   info.set_global();
   v8::internal::Parser parser(&info);
   parser.Parse(&info);
+  isolate->RequestGarbageCollectionForTesting(
+      v8::Isolate::kFullGarbageCollection);
   return 0;
 }

test/fuzzer/regexp.cc

@@ -71,5 +71,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
     Test(isolate, regexp, source, results_array);
   }
 
+  isolate->RequestGarbageCollectionForTesting(
+      v8::Isolate::kFullGarbageCollection);
   return 0;
 }