[wasm] Ensure serializability of JS_TO_WASM wrappers

On x64, we optimize out EmbeddedReferences, unless we explicitly
indicate serialization is enabled. We serialize js-to-wasm wrappers,
which include such references.

Bug: v8:7083
Change-Id: I976da4af74bf7ee3245e1465b8e47f2c042ec3b4
Reviewed-on: https://chromium-review.googlesource.com/780207Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Reviewed-by: Eric Holk <eholk@chromium.org>
Commit-Queue: Mircea Trofin <mtrofin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49546}

src/compiler/code-generator.cc

@@ -78,6 +78,11 @@ CodeGenerator::CodeGenerator(
   CreateFrameAccessState(frame);
   CHECK_EQ(info->is_osr(), osr_helper_.has_value());
   tasm_.set_jump_optimization_info(jump_opt);
+  Code::Kind code_kind = info_->code_kind();
+  if (code_kind == Code::JS_TO_WASM_FUNCTION ||
+      code_kind == Code::WASM_FUNCTION) {
+    tasm_.enable_serializer();
+  }
 }
 
 void CodeGenerator::AddProtectedInstructionLanding(uint32_t instr_offset,

src/isolate.h

@@ -1015,9 +1015,6 @@ class Isolate {
   }
 
   bool serializer_enabled() const { return serializer_enabled_; }
-  void set_serializer_enabled_for_test(bool serializer_enabled) {
-    serializer_enabled_ = serializer_enabled;
-  }
   bool snapshot_available() const {
     return snapshot_blob_ != nullptr && snapshot_blob_->raw_size != 0;
   }

test/cctest/wasm/test-run-wasm-module.cc

@@ -321,10 +321,6 @@ class WasmSerializationTest {
     WasmSerializationTest::BuildWireBytes(zone(), &buffer);
 
     Isolate* serialization_isolate = CcTest::InitIsolateOnce();
-    // Isolates do not have serialization enabled by default. We must enable it
-    // here or else the assembler will not mark external references so that the
-    // serializer can handle them correctly.
-    serialization_isolate->set_serializer_enabled_for_test(true);
     ErrorThrower thrower(serialization_isolate, "");
     uint8_t* bytes = nullptr;
     size_t bytes_size = 0;