Add a simpler key type for scratch resource keys.

bench/GrResourceCacheBench.cpp

Index: bench/GrResourceCacheBench.cpp
diff --git a/bench/GrResourceCacheBench.cpp b/bench/GrResourceCacheBench.cpp
index e30dd3052f4842448e971303c405b5d40dd560ec..491823b5b896e2103f0826bb1f01ac6ca3ae2f66 100644
--- a/bench/GrResourceCacheBench.cpp
+++ b/bench/GrResourceCacheBench.cpp
@@ -32,9 +32,8 @@ public:
         GrCacheID::Key key;
         memset(&key, 0, sizeof(key));
         key.fData32[0] = i;
-        static int gType = GrResourceKey::GenerateResourceType();
         static int gDomain = GrCacheID::GenerateDomain();
-        return GrResourceKey(GrCacheID(gDomain, key), gType, 0);
+        return GrResourceKey(GrCacheID(gDomain, key), 0);
     }