Cleanup resource flags

Converts GrResourceProvider::Flags and GrResourceCache::ScratchFlags
to "enum class" and fixes a case where we were accidentally using the
wrong type of flag. Makes sure to allocate GrSWMaskHelper proxies with
kNoPendingIO.

Bug: skia:8351
Change-Id: Ibcaa26314a53d0cb31ae22915ab94ab0fc07e76d
Reviewed-on: https://skia-review.googlesource.com/157280
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
diff --git a/tests/GrSurfaceTest.cpp b/tests/GrSurfaceTest.cpp
index f796187..bdec795 100644
--- a/tests/GrSurfaceTest.cpp
+++ b/tests/GrSurfaceTest.cpp
@@ -165,7 +165,7 @@
                     // Try directly creating the texture.
                     // Do this twice in an attempt to hit the cache on the second time through.
                     for (int i = 0; i < 2; ++i) {
-                        sk_sp<GrTextureProxy> proxy = proxyProvider->createInstantiatedProxy(
+                        auto proxy = proxyProvider->testingOnly_createInstantiatedProxy(
                                 desc, origin, fit, SkBudgeted::kYes);
                         if (!proxy) {
                             continue;