Remove unused copy-to-external YUV SkImage factories.

Also inline some helper functions into newer factory method
that are no longer shared.

Bug: skia:10632
Change-Id: I466c59f668d882802087acad1ec1f229505a3377
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/334596
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
diff --git a/RELEASE_NOTES.txt b/RELEASE_NOTES.txt
index 639605d..956a5bf 100644
--- a/RELEASE_NOTES.txt
+++ b/RELEASE_NOTES.txt
@@ -7,6 +7,17 @@
 Milestone 89
 ------------
 
+  * The following YUV image factories have been removed:
+    SkImage::MakeFromYUVTexturesCopyWithExternalBackend
+    SkImage::MakeFromNV12TexturesCopyWithExternalBackend
+    Replacement pattern outlined below.
+        1) Make image using MakeFromYUVATextures
+        2) Make a SkSurface around result texture using SkSurface::MakeFromBackendTexture
+        3) surface->getCanvas()->drawImage(image, 0, 0);
+        4) surface->flushAndSubmit()
+        5) Optional: SkImage::MakeFromBackendTexture() to use as SkImage.
+    https://review.skia.org/334596
+
   * Added a new interface for GrDirectContext creation in Metal, using
     a new struct called GrMtlBackendContext. The previous interface taking
     a MTLDevice and MTLCommandQueue is deprecated.