Rename *worstCase* to backingStore* in GrSurfaceProxy

These names are more appropriate after:

https://skia-review.googlesource.com/c/skia/+/241356 (Always create an approx-size texture for approx-fit proxies))

Note that this CL does have one substantive change in GrCoordTransform::hasSameEffectAs where we use our knowledge of the size at which the backing stores will be allocated to remove a sly usage of GrSurfaceProxy::underlyingUniqueID.

Change-Id: Ibbb8cb23c4503f267abbdf4794610f3262a6f515
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/250257
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
diff --git a/src/gpu/GrProxyProvider.cpp b/src/gpu/GrProxyProvider.cpp
index caaa800..d7fc8be 100644
--- a/src/gpu/GrProxyProvider.cpp
+++ b/src/gpu/GrProxyProvider.cpp
@@ -878,10 +878,10 @@
     // A proxy is functionally exact if:
     //   it is exact (obvs)
     //   when it is instantiated it will be exact (i.e., power of two dimensions)
-    //   it is already instantiated and the proxy covers the entire backing surface
+    //   when it is instantiated the content rect will cover the entire backing surface
     return proxy->priv().isExact() ||
            (!isInstantiated && SkIsPow2(proxy->width()) && SkIsPow2(proxy->height())) ||
-           (isInstantiated && proxy->worstCaseDimensions() == proxy->dimensions());
+           (proxy->backingStoreDimensions() == proxy->dimensions());
 }
 
 void GrProxyProvider::processInvalidUniqueKey(const GrUniqueKey& key, GrTextureProxy* proxy,