[heap] Fix TPH link-time errors with MSVC

Provide a stub `third_party_heap::Heap` implementation to work around
linker erors with Visual Studio.

cl.exe in debug mode seems to eliminate dead code not as aggressively
as clang or gcc, resulting in references to `third_party_heap::Heap`
remaining in unreachable code paths.

Refs: https://github.com/bnoordhuis/v8-cmake/issues/10
Bug: v8:10427
Change-Id: I61fde11697adc663b182f60c132eda435a7f11bd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2159490
Commit-Queue: Ben Noordhuis <info@bnoordhuis.nl>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Auto-Submit: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67293}

BUILD.gn

@@ -3126,6 +3126,8 @@ v8_source_set("v8_base_without_compiler") {
 
   if (v8_enable_third_party_heap) {
     sources += v8_third_party_heap_files
+  } else {
+    sources += [ "src/heap/third-party/heap-api-stub.cc" ]
   }
 
   if (v8_enable_wasm_gdb_remote_debugging) {

src/heap/third-party/heap-api-stub.cc

@@ -0,0 +1,53 @@
+// Copyright 2020 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 "src/execution/isolate-utils-inl.h"
+#include "src/heap/heap-inl.h"
+#include "src/heap/third-party/heap-api.h"
+
+namespace v8 {
+namespace internal {
+
+Isolate* Heap::GetIsolateFromWritableObject(HeapObject object) {
+  return GetHeapFromWritableObject(object)->isolate();
+}
+
+}  // namespace internal
+}  // namespace v8
+
+namespace v8 {
+namespace internal {
+namespace third_party_heap {
+
+// static
+std::unique_ptr<Heap> Heap::New(v8::internal::Isolate*) { return nullptr; }
+
+// static
+v8::internal::Isolate* Heap::GetIsolate(Address) { return nullptr; }
+
+AllocationResult Heap::Allocate(size_t, AllocationType, AllocationAlignment) {
+  return AllocationResult();
+}
+
+Address Heap::GetObjectFromInnerPointer(Address) { return 0; }
+
+const base::AddressRegion& Heap::GetCodeRange() {
+  static const base::AddressRegion no_region(0, 0);
+  return no_region;
+}
+
+// static
+bool Heap::InCodeSpace(Address) { return false; }
+
+// static
+bool Heap::InReadOnlySpace(Address) { return false; }
+
+// static
+bool Heap::IsValidHeapObject(HeapObject) { return false; }
+
+bool Heap::CollectGarbage() { return false; }
+
+}  // namespace third_party_heap
+}  // namespace internal
+}  // namespace v8