[wrapper-tracing] Enhance verifier output

third_party/WebKit/Source/bindings/core/v8/ScriptWrappableVisitorVerifier.h

Index: third_party/WebKit/Source/bindings/core/v8/ScriptWrappableVisitorVerifier.h
diff --git a/third_party/WebKit/Source/bindings/core/v8/ScriptWrappableVisitorVerifier.h b/third_party/WebKit/Source/bindings/core/v8/ScriptWrappableVisitorVerifier.h
index 4706b0dac75fab03ed96b60da2c0b8ecab83268d..8649e122d9723b287dba2815895ab1d99c12eca4 100644
--- a/third_party/WebKit/Source/bindings/core/v8/ScriptWrappableVisitorVerifier.h
+++ b/third_party/WebKit/Source/bindings/core/v8/ScriptWrappableVisitorVerifier.h
@@ -39,6 +39,7 @@ class ScriptWrappableVisitorVerifier : public WrapperVisitor {
   bool pushToMarkingDeque(
       void (*traceWrappersCallback)(const WrapperVisitor*, const void*),
       HeapObjectHeader* (*heapObjectHeaderCallback)(const void*),
+      void (*missedWriteBarrierCallback)(void),
       const void* object) const override {
     if (!heapObjectHeaderCallback(object)->isWrapperHeaderMarked()) {
       // If this branch is hit, it means that a white (not discovered by
@@ -48,9 +49,10 @@ class ScriptWrappableVisitorVerifier : public WrapperVisitor {
       // therefore its wrapper and all wrappers reachable from it would be
       // collected.
 
-      // Most often this means there is a write barrier missing somewhere.
-      // Check backtrace to see which classes are causing this and review all
-      // the places where white class is set to the black class.
+      // This means there is a write barrier missing somewhere. Check the
+      // backtrace to see which types are causing this and review all the
+      // places where white object is set to a black object.
+      missedWriteBarrierCallback();
       NOTREACHED();
     }
     traceWrappersCallback(this, object);