Fix sky include guards to match Chromium style

sky/engine/platform/graphics/gpu/WebGLImageConversion.h

 // Copyright 2014 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.
 
-#ifndef WebGLImageConversion_h
-#define WebGLImageConversion_h
+#ifndef SKY_ENGINE_PLATFORM_GRAPHICS_GPU_WEBGLIMAGECONVERSION_H_
+#define SKY_ENGINE_PLATFORM_GRAPHICS_GPU_WEBGLIMAGECONVERSION_H_
 
 #include "sky/engine/platform/PlatformExport.h"
 #include "sky/engine/platform/graphics/Image.h"
 #include "sky/engine/wtf/RefPtr.h"
 #include "third_party/khronos/GLES2/gl2.h"
 #include "third_party/khronos/GLES2/gl2ext.h"
 
 namespace blink {
 class Image;
 class IntSize;
@@ skipping 141 matching lines @@
     // data into the specified OpenGL destination format and type.
     // A sourceUnpackAlignment of zero indicates that the source
     // data is tightly packed. Non-zero values may take a slow path.
     // Destination data will have no gaps between rows.
     // Implemented in GraphicsContext3DImagePacking.cpp
     static bool packPixels(const uint8_t* sourceData, DataFormat sourceDataFormat, unsigned width, unsigned height, unsigned sourceUnpackAlignment, unsigned destinationFormat, unsigned destinationType, AlphaOp, void* destinationData, bool flipY);
 };
 
 } // namespace blink
 
-#endif // WebGLImageConversion_h
+#endif  // SKY_ENGINE_PLATFORM_GRAPHICS_GPU_WEBGLIMAGECONVERSION_H_