[PresentationAPI] Added/changed public/platform interfaces for start/joinSession

public/platform/modules/presentation/WebPresentationError.h

-// Copyright 2014 The Chromium Authors. All rights reserved.
+// Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef WebPushError_h
-#define WebPushError_h
+#ifndef WebPresentationError_h
+#define WebPresentationError_h
 
 #include "public/platform/WebString.h"
 
 namespace blink {
 
-struct WebPushError {
+struct WebPresentationError {
     enum ErrorType {
-        ErrorTypeAbort = 0,
-        ErrorTypeNetwork,
-        ErrorTypeNotFound,
+        ErrorTypeNoAvailableScreens = 0,
+        ErrorTypeSessionRequestCancelled,
+        ErrorTypeNoPresentationFound,
         ErrorTypeUnknown,
         ErrorTypeLast = ErrorTypeUnknown
     };
 
-    WebPushError(ErrorType errorType, const WebString& message)
+    WebPresentationError(ErrorType errorType, const WebString& message)
         : errorType(errorType)
         , message(message)
     {
     }
 
     ErrorType errorType;
     WebString message;
 };
 
 } // namespace blink
 
-#endif // WebPushError_h
+#endif // WebPresentationError_h