Switch SkImage's & SkImageGenerator's isValid call over to GrRecordingContext

This is another step towards replacing GrContext with the
GrDirectContext/GrRecordingContext pair.

Change-Id: I9336799a299e181fd56759f37dfed3da5da5d022
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/301856
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
diff --git a/gm/perspshaders.cpp b/gm/perspshaders.cpp
index 3092cdf..881f34c 100644
--- a/gm/perspshaders.cpp
+++ b/gm/perspshaders.cpp
@@ -150,7 +150,7 @@
     }
 
     void onDraw(SkCanvas* canvas) override {
-        if (!fImage || !fImage->isValid(canvas->getGrContext())) {
+        if (!fImage || !fImage->isValid(canvas->recordingContext())) {
             fImage = make_image(canvas, kCellSize, kCellSize);
         }