API functions returning Promises should not throw exceptions.

Source/bindings/core/v8/ExceptionState.cpp

Index: Source/bindings/core/v8/ExceptionState.cpp
diff --git a/Source/bindings/core/v8/ExceptionState.cpp b/Source/bindings/core/v8/ExceptionState.cpp
index 9db47f6be4bda2625aa6a4b48a73e22dda3f060d..f54d7a15b70304faaa317a651a94eedb770fe200 100644
--- a/Source/bindings/core/v8/ExceptionState.cpp
+++ b/Source/bindings/core/v8/ExceptionState.cpp
@@ -43,6 +43,13 @@ void ExceptionState::clearException()
     m_exception.clear();
 }
 
+ScriptPromise ExceptionState::reject(ScriptState* scriptState)
+{
+    ScriptPromise promise = ScriptPromise::reject(scriptState, m_exception.newLocal(scriptState->isolate()));
+    clearException();
+    return promise;
+}
+
 void ExceptionState::throwDOMException(const ExceptionCode& ec, const String& message)
 {
     ASSERT(ec);