move SkImageInfo into its own header

BUG=
R=djsollen@google.com

Review URL: https://codereview.chromium.org/71813002

git-svn-id: http://skia.googlecode.com/svn/trunk/gyp@12273 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/core.gypi b/core.gypi
index 3000c70..e31b8ff 100644
--- a/core.gypi
+++ b/core.gypi
@@ -219,7 +219,6 @@
 
         '<(skia_include_path)/core/Sk64.h',
         '<(skia_include_path)/core/SkAdvancedTypefaceMetrics.h',
-        '<(skia_include_path)/core/SkAlpha.h',
         '<(skia_include_path)/core/SkBitmap.h',
         '<(skia_include_path)/core/SkBitmapDevice.h',
         '<(skia_include_path)/core/SkBlitRow.h',
@@ -255,6 +254,7 @@
         '<(skia_include_path)/core/SkImageEncoder.h',
         '<(skia_include_path)/core/SkImageFilter.h',
         '<(skia_include_path)/core/SkImageFilterUtils.h',
+        '<(skia_include_path)/core/SkImageInfo.h',
         '<(skia_include_path)/core/SkInstCnt.h',
         '<(skia_include_path)/core/SkMallocPixelRef.h',
         '<(skia_include_path)/core/SkMask.h',