Introduce the nested namespace ::blink::cssvalue, start with CSSColorValue.

third_party/WebKit/Source/core/css/CSSColorValue.cpp

 // Copyright 2016 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 "core/css/CSSColorValue.h"
 
 #include "core/css/CSSValuePool.h"
 
 namespace blink {
+namespace cssvalue {
 
 CSSColorValue* CSSColorValue::create(RGBA32 color) {
   // These are the empty and deleted values of the hash table.
   if (color == Color::transparent)
     return cssValuePool().transparentColor();
   if (color == Color::white)
     return cssValuePool().whiteColor();
   // Just because it is common.
   if (color == Color::black)
     return cssValuePool().blackColor();
 
   CSSValuePool::ColorValueCache::AddResult entry =
       cssValuePool().getColorCacheEntry(color);
   if (entry.isNewEntry)
     entry.storedValue->value = new CSSColorValue(color);
   return entry.storedValue->value;
 }
 
+}  // namespace cssvalue
 }  // namespace blink