[wrapper-tracing] Support for incrementally tracing ScopedPersistent

third_party/WebKit/Source/bindings/core/v8/ScriptWrappableVisitor.cpp

Index: third_party/WebKit/Source/bindings/core/v8/ScriptWrappableVisitor.cpp
diff --git a/third_party/WebKit/Source/bindings/core/v8/ScriptWrappableVisitor.cpp b/third_party/WebKit/Source/bindings/core/v8/ScriptWrappableVisitor.cpp
index 82a6d73e9c431cc7d6bf916e06120677e6f05d3a..e2692fa0fe0846c3e6580205c20d91b7be467678 100644
--- a/third_party/WebKit/Source/bindings/core/v8/ScriptWrappableVisitor.cpp
+++ b/third_party/WebKit/Source/bindings/core/v8/ScriptWrappableVisitor.cpp
@@ -6,6 +6,7 @@
 
 #include "bindings/core/v8/ActiveScriptWrappable.h"
 #include "bindings/core/v8/DOMWrapperWorld.h"
+#include "bindings/core/v8/ScopedPersistent.h"
 #include "bindings/core/v8/ScriptWrappableVisitorVerifier.h"
 #include "bindings/core/v8/V8AbstractEventListener.h"
 #include "bindings/core/v8/WrapperTypeInfo.h"
@@ -211,16 +212,33 @@ void ScriptWrappableVisitor::markWrappersInAllWorlds(
       const_cast<ScriptWrappable*>(scriptWrappable), this, m_reporter);
 }
 
-void ScriptWrappableVisitor::traceWrappers(
-    const ScopedPersistent<v8::Value>* scopedPersistent) const {
-  markWrapper(
-      &(const_cast<ScopedPersistent<v8::Value>*>(scopedPersistent)->get()));
+void ScriptWrappableVisitor::writeBarrier(
+    const void* srcObject,
+    const TraceWrapperScopedPersistent<v8::Value>* dstObject) {
+  if (!RuntimeEnabledFeatures::traceWrappablesEnabled()) {
+    return;
+  }
+  if (!srcObject || !dstObject) {

[Marcel Hlopko, 2016/11/02 16:44:51]

|| !dstObject->handle?

Or dcheck in TraceWrapperScopedPersistent.set?

[Michael Lippautz, 2016/11/02 17:07:55]

Done, here, since we have the full type definition.

+    return;
+  }
+  // We only require a write barrier if |srcObject|  is already marked. Note
+  // that this implicitly disabled the write barrier when  wrapper tracing

[Marcel Hlopko, 2016/11/02 16:44:51]

...this *is* implicitly...

[Michael Lippautz, 2016/11/02 17:07:55]

Rewrote as ... this implicitly disables the write barrier...

+  // is not active as object will not be marked in this case.
+  if (!HeapObjectHeader::fromPayload(srcObject)->isWrapperHeaderMarked()) {
+    return;
+  }
+
+  currentVisitor(ThreadState::current()->isolate())
+      ->markWrapper(
+          &(const_cast<TraceWrapperScopedPersistent<v8::Value>*>(dstObject)
+                ->get()));
 }
 
 void ScriptWrappableVisitor::traceWrappers(
-    const ScopedPersistent<v8::Object>* scopedPersistent) const {
+    const TraceWrapperScopedPersistent<v8::Value>* tracedPersistent) const {
   markWrapper(
-      &(const_cast<ScopedPersistent<v8::Object>*>(scopedPersistent)->get()));
+      &(const_cast<TraceWrapperScopedPersistent<v8::Value>*>(tracedPersistent)
+            ->get()));
 }
 
 void ScriptWrappableVisitor::markWrapper(
@@ -229,11 +247,11 @@ void ScriptWrappableVisitor::markWrapper(
   handle->RegisterExternalReference(m_reporter);
 }
 
-void ScriptWrappableVisitor::markWrapper(
-    const v8::PersistentBase<v8::Object>* handle) const {
-  DCHECK(m_reporter);
-  handle->RegisterExternalReference(m_reporter);
-}
+// void ScriptWrappableVisitor::markWrapper(
+//     const v8::PersistentBase<v8::Object>* handle) const {
+//   DCHECK(m_reporter);

[Marcel Hlopko, 2016/11/02 16:44:51]

delete commented out code?

[Michael Lippautz, 2016/11/02 17:07:55]

Already gone.

+//   handle->RegisterExternalReference(m_reporter);
+// }
 
 void ScriptWrappableVisitor::dispatchTraceWrappers(
     const TraceWrapperBase* wrapperBase) const {