API functions returning Promises should not throw exceptions.

Source/bindings/core/v8/ExceptionState.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 25 matching lines @@
 #include "core/dom/ExceptionCode.h"
 
 namespace blink {
 
 void ExceptionState::clearException()
 {
     m_code = 0;
     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);
     ASSERT(m_isolate);
     ASSERT(!m_creationContext.IsEmpty());
 
     // SecurityError is thrown via ::throwSecurityError, and _careful_ consideration must be given to the data exposed to JavaScript via the 'sanitizedMessage'.
     ASSERT(ec != SecurityError);
 
     m_code = ec;
@@ skipping 123 matching lines @@
             processedMessage = ExceptionMessages::failedToDeleteIndexed(interfaceName(), message);
         else if (m_context == IndexedGetterContext)
             processedMessage = ExceptionMessages::failedToGetIndexed(interfaceName(), message);
         else if (m_context == IndexedSetterContext)
             processedMessage = ExceptionMessages::failedToSetIndexed(interfaceName(), message);
     }
     return processedMessage;
 }
 
 } // namespace blink