Fix sky include guards to match Chromium style

sky/engine/platform/PurgeableVector.h

 /*
  * Copyright (C) 2014 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 10 matching lines @@
  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef PurgeableVector_h
-#define PurgeableVector_h
+#ifndef SKY_ENGINE_PLATFORM_PURGEABLEVECTOR_H_
+#define SKY_ENGINE_PLATFORM_PURGEABLEVECTOR_H_
 
 #include "sky/engine/platform/PlatformExport.h"
 #include "sky/engine/wtf/Forward.h"
 #include "sky/engine/wtf/Noncopyable.h"
 #include "sky/engine/wtf/Vector.h"
 
 namespace blink {
 
 class WebDiscardableMemory;
 
@@ skipping 70 matching lines @@
     Vector<char> m_vector;
     OwnPtr<WebDiscardableMemory> m_discardable;
     size_t m_discardableCapacity;
     size_t m_discardableSize;
     bool m_isPurgeable;
     int m_locksCount;
 };
 
 } // namespace blink
 
-#endif // PurgeableVector_h
+#endif  // SKY_ENGINE_PLATFORM_PURGEABLEVECTOR_H_