Add error struct to support the setSinkId operation for WebMediaPlayer.

public/platform/WebSetSinkIdError.h

Index: public/platform/WebSetSinkIdError.h
diff --git a/public/platform/modules/background_sync/WebSyncError.h b/public/platform/WebSetSinkIdError.h
similarity index 53%
copy from public/platform/modules/background_sync/WebSyncError.h
copy to public/platform/WebSetSinkIdError.h
index cf537ad304dd119a19d82831846dafced3270600..557c48873748224c4cbd61fcd2b43af0899365d3 100644
--- a/public/platform/modules/background_sync/WebSyncError.h
+++ b/public/platform/WebSetSinkIdError.h
@@ -2,23 +2,23 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef WebSyncError_h
-#define WebSyncError_h
+#ifndef WebSetSinkIdError_h
+#define WebSetSinkIdError_h
 
 #include "public/platform/WebString.h"
 
 namespace blink {
 
-struct WebSyncError {
+struct WebSetSinkIdError {
     enum ErrorType {
-        ErrorTypeAbort = 0,
-        ErrorTypeNoPermission,
-        ErrorTypeNotFound,
-        ErrorTypeUnknown,
-        ErrorTypeLast = ErrorTypeUnknown
+        ErrorTypeNotFound = 1,
+        ErrorTypeSecurity,
+        ErrorTypeAbort,
+        ErrorTypeNotSupported,
+        ErrorTypeLast = ErrorTypeNotSupported
     };
 
-    WebSyncError(ErrorType errorType, const WebString& message)
+    WebSetSinkIdError(ErrorType errorType, const WebString& message)
         : errorType(errorType)
         , message(message)
     {
@@ -30,4 +30,4 @@ struct WebSyncError {
 
 } // namespace blink
 
-#endif // WebSyncError_h
+#endif // WebSetSinkIdError_h