Add ability to remove unique key from proxy and underlying surface.

Bug: skia:
Change-Id: I66b891ce9ca35906fdbddb36f565b35b25825112
Reviewed-on: https://skia-review.googlesource.com/51240
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
diff --git a/src/gpu/GrSoftwarePathRenderer.cpp b/src/gpu/GrSoftwarePathRenderer.cpp
index c9377e2..8b50908 100644
--- a/src/gpu/GrSoftwarePathRenderer.cpp
+++ b/src/gpu/GrSoftwarePathRenderer.cpp
@@ -290,7 +290,7 @@
 
     sk_sp<GrTextureProxy> proxy;
     if (useCache) {
-        proxy = fResourceProvider->findProxyByUniqueKey(maskKey, kTopLeft_GrSurfaceOrigin);
+        proxy = fResourceProvider->findOrCreateProxyByUniqueKey(maskKey, kTopLeft_GrSurfaceOrigin);
     }
     if (!proxy) {
         SkBackingFit fit = useCache ? SkBackingFit::kExact : SkBackingFit::kApprox;