Streams: Put binding originals behind a flag

Copying MessageChannel and other functions to the binding object caused
a memory regression. As a temporary workaround, only copy them to the
binding object when the TransferableStreams feature is enabled.

BUG=897046,900141,899637

Change-Id: If312f2e0967a19e9db427f60125d96c48d45fdc7
Reviewed-on: https://chromium-review.googlesource.com/c/1307534Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Commit-Queue: Adam Rice <ricea@chromium.org>
Cr-Commit-Position: refs/heads/master@{#604178}

third_party/blink/renderer/bindings/core/v8/initialize_v8_extras_binding.cc

@@ -15,6 +15,7 @@
 #include "third_party/blink/renderer/platform/bindings/to_v8.h"
 #include "third_party/blink/renderer/platform/bindings/v8_binding.h"
 #include "third_party/blink/renderer/platform/bindings/v8_throw_exception.h"
+#include "third_party/blink/renderer/platform/runtime_enabled_features.h"
 #include "v8/include/v8.h"
 
 namespace blink {
@@ -87,6 +88,10 @@ void AddCountUse(ScriptState* script_state, v8::Local<v8::Object> binding) {
 }
 
 void AddOriginals(ScriptState* script_state, v8::Local<v8::Object> binding) {
+  // These values are only used when serialization is enabled.
+  if (!RuntimeEnabledFeatures::TransferableStreamsEnabled())
+    return;
+
   v8::Local<v8::Object> global = script_state->GetContext()->Global();
   v8::Local<v8::Context> context = script_state->GetContext();
   v8::Isolate* isolate = script_state->GetIsolate();

third_party/blink/renderer/core/streams/readable_stream_operations.cc

@@ -13,6 +13,7 @@
 #include "third_party/blink/renderer/core/streams/underlying_source_base.h"
 #include "third_party/blink/renderer/platform/bindings/exception_state.h"
 #include "third_party/blink/renderer/platform/bindings/script_state.h"
+#include "third_party/blink/renderer/platform/runtime_enabled_features.h"
 #include "third_party/blink/renderer/platform/wtf/assertions.h"
 
 namespace blink {
@@ -271,6 +272,7 @@ MessagePort* ReadableStreamOperations::ReadableStreamSerialize(
     ScriptValue stream,
     ExceptionState& exception_state) {
   DCHECK(IsReadableStreamForDCheck(script_state, stream));
+  DCHECK(RuntimeEnabledFeatures::TransferableStreamsEnabled());
   v8::TryCatch block(script_state->GetIsolate());
   v8::Local<v8::Value> args[] = {stream.V8Value()};
   ScriptValue result(
@@ -297,6 +299,7 @@ ScriptValue ReadableStreamOperations::ReadableStreamDeserialize(
     MessagePort* port,
     ExceptionState& exception_state) {
   DCHECK(port);
+  DCHECK(RuntimeEnabledFeatures::TransferableStreamsEnabled());
   auto* isolate = script_state->GetIsolate();
   v8::Local<v8::Context> context = script_state->GetContext();
   v8::Local<v8::Value> port_v8 = ToV8(port, context->Global(), isolate);

third_party/blink/renderer/core/streams/readable_stream_operations_test.cc

@@ -19,6 +19,7 @@
 #include "third_party/blink/renderer/platform/bindings/v8_binding_macros.h"
 #include "third_party/blink/renderer/platform/bindings/v8_throw_exception.h"
 #include "third_party/blink/renderer/platform/heap/handle.h"
+#include "third_party/blink/renderer/platform/runtime_enabled_features.h"
 #include "third_party/blink/renderer/platform/testing/unit_test_helpers.h"
 #include "v8/include/v8.h"
 
@@ -494,6 +495,8 @@ TEST(ReadableStreamOperationsTest, Tee) {
 }
 
 TEST(ReadableStreamOperationsTest, Serialize) {
+  RuntimeEnabledFeatures::SetTransferableStreamsEnabled(true);
+
   V8TestingScope scope;
   TryCatchScope try_catch_scope(scope.GetIsolate());
   ScriptValue original = EvalWithPrintingError(&scope,

third_party/blink/renderer/platform/runtime_enabled_features.json5

@@ -1256,6 +1256,9 @@
     {
       name: "TrackLayoutPassesPerBlock",
     },
+    {
+      name: "TransferableStreams",
+    },
     {
       name: "TrustedDOMTypes",
       status: "experimental",