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 241c6f8211309f711923a7cc0b60d966232a02ce..c31c997bbfa87d3d737f1f0e063bf617b5d8bb52 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);