Avoid unneeded picture shader color space transforms

Also update SkPictureImageFilter to use SkColorSpace::Equals instead of
direct comparison.

Change-Id: I434cd6d1afcb869d2a56601b72edf56d207d9868
Reviewed-on: https://skia-review.googlesource.com/23201
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
diff --git a/src/effects/SkPictureImageFilter.cpp b/src/effects/SkPictureImageFilter.cpp
index 80361aa..da3204e 100644
--- a/src/effects/SkPictureImageFilter.cpp
+++ b/src/effects/SkPictureImageFilter.cpp
@@ -137,7 +137,7 @@
 
 sk_sp<SkImageFilter> SkPictureImageFilter::onMakeColorSpace(SkColorSpaceXformer* xformer) const {
     sk_sp<SkColorSpace> dstCS = xformer->dst();
-    if (dstCS == fColorSpace) {
+    if (SkColorSpace::Equals(dstCS.get(), fColorSpace.get())) {
         return this->refMe();
     }