Remove redundant IsEmpty checks after calling toV8()

third_party/WebKit/Source/bindings/core/v8/V8V0CustomElementLifecycleCallbacks.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 129 matching lines @@
 
     if (!m_scriptState->contextIsValid())
         return;
 
     element->setV0CustomElementState(Element::V0Upgraded);
 
     ScriptState::Scope scope(m_scriptState.get());
     v8::Isolate* isolate = m_scriptState->isolate();
     v8::Local<v8::Context> context = m_scriptState->context();
     v8::Local<v8::Value> receiverValue = toV8(element, context->Global(), isolate);
-    if (receiverValue.IsEmpty())
-        return;
     v8::Local<v8::Object> receiver = receiverValue.As<v8::Object>();
 
     // Swizzle the prototype of the wrapper.
     v8::Local<v8::Object> prototype = m_prototype.newLocal(isolate);
     if (prototype.IsEmpty())
         return;
     if (!v8CallBoolean(receiver->SetPrototype(context, prototype)))
         return;
 
     v8::Local<v8::Function> callback = m_created.newLocal(isolate);
@@ skipping 22 matching lines @@
     // Bug 329665 tracks similar behavior for other synchronous events.
     if (!getExecutionContext() || getExecutionContext()->activeDOMObjectsAreStopped())
         return;
 
     if (!m_scriptState->contextIsValid())
         return;
     ScriptState::Scope scope(m_scriptState.get());
     v8::Isolate* isolate = m_scriptState->isolate();
     v8::Local<v8::Context> context = m_scriptState->context();
     v8::Local<v8::Value> receiver = toV8(element, context->Global(), isolate);
-    if (receiver.IsEmpty())
-        return;
-
     v8::Local<v8::Function> callback = m_attributeChanged.newLocal(isolate);
-    if (callback.IsEmpty())

[Yuki, 2016/08/24 12:02:08]

It seems not guaranteed to me that m_attributeChanged never be empty.
It seems to me that m_attributeChanged is a kind of optional field and we can
make this empty.

If not, can we add CHECK(!m_attributeChanged.IsEmpty()) in the constructor?

If so, we'd like to put this check earlier.

-        return;
-
     v8::Local<v8::Value> argv[] = {
         v8String(isolate, name),
         oldValue.isNull() ? v8::Local<v8::Value>(v8::Null(isolate)) : v8::Local<v8::Value>(v8String(isolate, oldValue)),
         newValue.isNull() ? v8::Local<v8::Value>(v8::Null(isolate)) : v8::Local<v8::Value>(v8String(isolate, newValue))
     };
 
     v8::TryCatch exceptionCatcher(isolate);
     exceptionCatcher.SetVerbose(true);
     V8ScriptRunner::callFunction(callback, getExecutionContext(), receiver, WTF_ARRAY_LENGTH(argv), argv, isolate);
 }
 
 void V8V0CustomElementLifecycleCallbacks::call(const ScopedPersistent<v8::Function>& weakCallback, Element* element)
 {
     // FIXME: callbacks while paused should be queued up for execution to
     // continue then be delivered in order rather than delivered immediately.
     // Bug 329665 tracks similar behavior for other synchronous events.
     if (!getExecutionContext() || getExecutionContext()->activeDOMObjectsAreStopped())
         return;
 
     if (!m_scriptState->contextIsValid())
         return;
     ScriptState::Scope scope(m_scriptState.get());
     v8::Isolate* isolate = m_scriptState->isolate();
     v8::Local<v8::Context> context = m_scriptState->context();
     v8::Local<v8::Function> callback = weakCallback.newLocal(isolate);
     if (callback.IsEmpty())
         return;
 
     v8::Local<v8::Value> receiver = toV8(element, context->Global(), isolate);
-    if (receiver.IsEmpty())
-        return;
-
     v8::TryCatch exceptionCatcher(isolate);
     exceptionCatcher.SetVerbose(true);
     V8ScriptRunner::callFunction(callback, getExecutionContext(), receiver, 0, 0, isolate);
 }
 
 DEFINE_TRACE(V8V0CustomElementLifecycleCallbacks)
 {
     V0CustomElementLifecycleCallbacks::trace(visitor);
     ContextLifecycleObserver::trace(visitor);
 }
 
 } // namespace blink