Move PageTransition into content namespace. While I'm touching all these files, I've also updated...

content/common/page_transition_types.cc

-// Copyright (c) 2010 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/page_transition_types.h"
-
-#include "base/logging.h"
-
-// static
-PageTransition::Type PageTransition::FromInt(int32 type) {
-  if (!ValidType(type)) {
-    NOTREACHED() << "Invalid transition type " << type;
-
-    // Return a safe default so we don't have corrupt data in release mode.
-    return LINK;
-  }
-  return static_cast<Type>(type);
-}
-
-// static
-const char* PageTransition::CoreTransitionString(Type type) {
-  switch (type & PageTransition::CORE_MASK) {
-    case 0: return "link";
-    case 1: return "typed";
-    case 2: return "auto_bookmark";
-    case 3: return "auto_subframe";
-    case 4: return "manual_subframe";
-    case 5: return "generated";
-    case 6: return "start_page";
-    case 7: return "form_submit";
-    case 8: return "reload";
-    case 9: return "keyword";
-    case 10: return "keyword_generated";
-  }
-  return NULL;
-}