Remove some uses of GrSurface::config()

Bug: skia:6718

Change-Id: I71ad95f910b6434e4d9a01c2750f1b2b08b2f6c4
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/233567
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
diff --git a/src/gpu/gl/GrGLRenderTarget.cpp b/src/gpu/gl/GrGLRenderTarget.cpp
index d588335..5dc7e04 100644
--- a/src/gpu/gl/GrGLRenderTarget.cpp
+++ b/src/gpu/gl/GrGLRenderTarget.cpp
@@ -86,7 +86,7 @@
 GrBackendRenderTarget GrGLRenderTarget::getBackendRenderTarget() const {
     GrGLFramebufferInfo fbi;
     fbi.fFBOID = fRTFBOID;
-    fbi.fFormat = this->getGLGpu()->glCaps().configSizedInternalFormat(this->config());
+    fbi.fFormat = GrGLFormatToEnum(this->format());
     int numStencilBits = 0;
     if (GrStencilAttachment* stencil = this->renderTargetPriv().getStencilAttachment()) {
         numStencilBits = stencil->bits();