Revert "Pass in a SkColorType into SkImage_Gpu ctor."

This reverts commit 1d17543133c023da03f1ef4ab0a125ca3782957c.

Reason for revert: android bots

Original change's description:
> Pass in a SkColorType into SkImage_Gpu ctor.
> 
> This allows us to get rid of using the GrPixelConfig on proxy to create
> the SkColorType
> 
> Bug: skia:6718
> Change-Id: I1758b79152fa1e8a1796e55d19f5e8ca0b0e8b7b
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/264396
> Commit-Queue: Greg Daniel <egdaniel@google.com>
> Reviewed-by: Robert Phillips <robertphillips@google.com>

TBR=egdaniel@google.com,robertphillips@google.com

Change-Id: I449e6b0750d611346791beb1dd1346106ad01741
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:6718
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/264469
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
diff --git a/src/gpu/GrContextPriv.cpp b/src/gpu/GrContextPriv.cpp
index e033ffa..7fd443b 100644
--- a/src/gpu/GrContextPriv.cpp
+++ b/src/gpu/GrContextPriv.cpp
@@ -131,10 +131,9 @@
         return nullptr;
     }
 
-    SkColorType colorType = GrColorTypeToSkColorType(GrMaskFormatToColorType(format));
     SkASSERT(views[index].proxy()->priv().isExact());
     sk_sp<SkImage> image(new SkImage_Gpu(sk_ref_sp(fContext), kNeedNewImageUniqueID,
-                                         views[index], colorType, kPremul_SkAlphaType, nullptr));
+                                         kPremul_SkAlphaType, views[index], nullptr));
     return image;
 }