Moved the following IPC messages used by the chrome NPAPI plugin installer out of content

content/common/content_constants.cc

 // Copyright (c) 2006-2008 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/common/content_constants.h"
 
 namespace content {
 
 // This number used to be limited to 32 in the past (see b/535234).
 const unsigned int kMaxRendererProcessCount = 42;
 const int kMaxSessionHistoryEntries = 50;
 const size_t kMaxTitleChars = 4 * 1024;
 const size_t kMaxURLChars = 2 * 1024 * 1024;
 const size_t kMaxURLDisplayChars = 32 * 1024;
 
+const char kDefaultPluginRenderViewId[] = "PluginRenderViewId";
+const char kDefaultPluginRenderProcessId[] = "PluginRenderProcessId";
+
 }  // namespace content
 
 #undef FPL