createElement should not transmit exceptions but report them.

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

Index: third_party/WebKit/Source/bindings/core/v8/ScriptCustomElementDefinition.cpp
diff --git a/third_party/WebKit/Source/bindings/core/v8/ScriptCustomElementDefinition.cpp b/third_party/WebKit/Source/bindings/core/v8/ScriptCustomElementDefinition.cpp
index d782e5a2ab816bd76825718e8cf2c863e1816c2d..cdf2d1a7bbb145770e39aebeabc5d133012ec427 100644
--- a/third_party/WebKit/Source/bindings/core/v8/ScriptCustomElementDefinition.cpp
+++ b/third_party/WebKit/Source/bindings/core/v8/ScriptCustomElementDefinition.cpp
@@ -151,23 +151,48 @@ ScriptCustomElementDefinition::ScriptCustomElementDefinition(
       m_scriptState(scriptState),
       m_constructor(scriptState->isolate(), constructor) {}
 
-HTMLElement* ScriptCustomElementDefinition::createElementSync(
+static void dispatchErrorEvent(v8::Isolate* isolate,
+                               v8::Local<v8::Value> exception,
+                               v8::Local<v8::Object> constructor) {
+  v8::TryCatch tryCatch(isolate);
+  tryCatch.SetVerbose(true);
+  V8ScriptRunner::throwException(
+      isolate, exception, constructor.As<v8::Function>()->GetScriptOrigin());
+}
+
+HTMLElement* ScriptCustomElementDefinition::handleCreateElementSyncException(
     Document& document,
     const QualifiedName& tagName,
+    v8::Isolate* isolate,
     ExceptionState& exceptionState) {
-  DCHECK(ScriptState::current(m_scriptState->isolate()) == m_scriptState);
+  DCHECK(exceptionState.hadException());
+  // 6.1."If any of these subsubsteps threw an exception".1
+  // Report the exception.
+  dispatchErrorEvent(isolate, exceptionState.getException(), constructor());
+  exceptionState.clearException();
+  // ... .2 Return HTMLUnknownElement.
+  return CustomElement::createFailedElement(document, tagName);
+}
+
+HTMLElement* ScriptCustomElementDefinition::createElementSync(
+    Document& document,
+    const QualifiedName& tagName) {
+  if (!m_scriptState->contextIsValid())
+    return CustomElement::createFailedElement(document, tagName);
+  ScriptState::Scope scope(m_scriptState.get());
+  v8::Isolate* isolate = m_scriptState->isolate();
 
-  // Create an element
+  ExceptionState exceptionState(ExceptionState::ConstructionContext,
+                                "CustomElement", constructor(), isolate);
+
+  // Create an element with the synchronous custom elements flag set.
   // https://dom.spec.whatwg.org/#concept-create-element
-  // 6. If definition is non-null
-  // 6.1. If the synchronous custom elements flag is set:
-  // 6.1.2. Set result to Construct(C). Rethrow any exceptions.
 
   // Create an element and push to the construction stack.
   // V8HTMLElement::constructorCustom() can only refer to
   // window.document(), but it is different from the document here
-  // when it is an import document.  This is not exactly what the
-  // spec defines, but the public behavior matches to the spec.
+  // when it is an import document. This is not exactly what the
+  // spec defines, but the non-imports behavior matches to the spec.
   Element* element = createElementForConstructor(document);
   {
     ConstructionStackScope constructionStackScope(this, element);
@@ -175,51 +200,19 @@ HTMLElement* ScriptCustomElementDefinition::createElementSync(
     element = runConstructor();
     if (tryCatch.HasCaught()) {
       exceptionState.rethrowV8Exception(tryCatch.Exception());
-      return nullptr;
+      return handleCreateElementSyncException(document, tagName, isolate,
+                                              exceptionState);
     }
   }
 
   // 6.1.3. through 6.1.9.
   checkConstructorResult(element, document, tagName, exceptionState);
-  if (exceptionState.hadException())
-    return nullptr;
-
-  DCHECK_EQ(element->getCustomElementState(), CustomElementState::Custom);
-  return toHTMLElement(element);
-}
-
-static void dispatchErrorEvent(v8::Isolate* isolate,
-                               v8::Local<v8::Value> exception,
-                               v8::Local<v8::Object> constructor) {
-  v8::TryCatch tryCatch(isolate);
-  tryCatch.SetVerbose(true);
-  V8ScriptRunner::throwException(
-      isolate, exception, constructor.As<v8::Function>()->GetScriptOrigin());
-}
-
-HTMLElement* ScriptCustomElementDefinition::createElementSync(
-    Document& document,
-    const QualifiedName& tagName) {
-  ScriptState::Scope scope(m_scriptState.get());
-  v8::Isolate* isolate = m_scriptState->isolate();
-
-  // When invoked from "create an element for a token":
-  // https://html.spec.whatwg.org/multipage/syntax.html#create-an-element-for-the-token
-
-  ExceptionState exceptionState(ExceptionState::ConstructionContext,
-                                "CustomElement", constructor(), isolate);
-  HTMLElement* element = createElementSync(document, tagName, exceptionState);
-
   if (exceptionState.hadException()) {
-    DCHECK(!element);
-    // 7. If this step throws an exception, then report the exception, ...
-    dispatchErrorEvent(isolate, exceptionState.getException(), constructor());
-    exceptionState.clearException();
-    // and return HTMLUnknownElement.
-    return CustomElement::createFailedElement(document, tagName);
+    return handleCreateElementSyncException(document, tagName, isolate,
+                                            exceptionState);
   }
-  DCHECK(element);
-  return element;
+  DCHECK_EQ(element->getCustomElementState(), CustomElementState::Custom);
+  return toHTMLElement(element);
 }
 
 // https://html.spec.whatwg.org/multipage/scripting.html#upgrades