Move WGL header from include to src

NOTRY=true

Review URL: https://codereview.chromium.org/728823002
diff --git a/gyp/utils.gypi b/gyp/utils.gypi
index 5148491..8ec0807 100644
--- a/gyp/utils.gypi
+++ b/gyp/utils.gypi
@@ -38,7 +38,6 @@
         '<(skia_include_path)/utils/SkRTConf.h',
         '<(skia_include_path)/utils/SkProxyCanvas.h',
         '<(skia_include_path)/utils/SkTextBox.h',
-        '<(skia_include_path)/utils/SkWGL.h',
 
         '<(skia_src_path)/utils/SkBase64.cpp',
         '<(skia_src_path)/utils/SkBase64.h',
@@ -127,6 +126,7 @@
         '<(skia_src_path)/utils/win/SkDWriteGeometrySink.h',
         '<(skia_src_path)/utils/win/SkHRESULT.cpp',
         '<(skia_src_path)/utils/win/SkIStream.cpp',
+        '<(skia_src_path)/utils/win/SkWGL.h',
         '<(skia_src_path)/utils/win/SkWGL_win.cpp',
 
         #testing