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/src@12273 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/image/SkImage.cpp b/image/SkImage.cpp
index c8559e6..39fd93a 100644
--- a/image/SkImage.cpp
+++ b/image/SkImage.cpp
@@ -12,14 +12,6 @@
 
 SK_DEFINE_INST_COUNT(SkImage)
 
-bool operator==(const SkImageInfo& lhs, const SkImageInfo& rhs) {
-    return 0 == memcmp(&lhs, &rhs, sizeof(SkImageInfo));
-}
-bool operator!=(const SkImageInfo& lhs, const SkImageInfo& rhs) {
-    return 0 != memcmp(&lhs, &rhs, sizeof(SkImageInfo));
-}
-
-
 static SkImage_Base* as_IB(SkImage* image) {
     return static_cast<SkImage_Base*>(image);
 }