[PresentationAPI] Implementing send() from WebPresentationClient to the PresentationService.

content/public/common/presentation_constants.cc

 // 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.
 
-#include "content/public/browser/interstitial_page_delegate.h"
+#include "content/public/common/presentation_constants.h"
 
 namespace content {
-InterstitialPageDelegate::TypeID InterstitialPageDelegate::GetTypeForTesting()
-    const {
-  return nullptr;
-}
+
+const size_t kMaxPresentationSessionMessageSize = 64 * 1024; // 64 KB.
 
 }  // namespace content