Revert "Have a GrBackendFormat be stored on gpu proxies."

This reverts commit 51b1c12bbc2fa3f8d4faa29ad19c6f3cb34837ce.

Reason for revert: reverting till flutter gets to 1.1 to fix build issues.

Original change's description:
> Have a GrBackendFormat be stored on gpu proxies.
>
> Bug: skia:
> Change-Id: Iaf1fb24ab29a61d44e5fa59a5e0867ed02dcda90
> Reviewed-on: https://skia-review.googlesource.com/c/168021
> Reviewed-by: Brian Osman <brianosman@google.com>
> Commit-Queue: Greg Daniel <egdaniel@google.com>

TBR=egdaniel@google.com,bsalomon@google.com,brianosman@google.com

Change-Id: I574fdc084ef5994596c51fb0d60423b5dc01b885
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:903701 chromium:903756
Reviewed-on: https://skia-review.googlesource.com/c/169835
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
diff --git a/src/gpu/SkGr.cpp b/src/gpu/SkGr.cpp
index 0a6033e..168cce6 100644
--- a/src/gpu/SkGr.cpp
+++ b/src/gpu/SkGr.cpp
@@ -160,13 +160,8 @@
     desc.fConfig = baseProxy->config();
     desc.fSampleCnt = 1;
 
-    GrBackendFormat format = baseProxy->backendFormat().makeTexture2D();
-    if (!format.isValid()) {
-        return nullptr;
-    }
-
     sk_sp<GrTextureProxy> proxy =
-            proxyProvider->createMipMapProxy(format, desc, baseProxy->origin(), SkBudgeted::kYes);
+            proxyProvider->createMipMapProxy(desc, baseProxy->origin(), SkBudgeted::kYes);
     if (!proxy) {
         return nullptr;
     }