Use SkAutoSTMalloc in GrResourceKey

TBR=robertphillips@google.com

Review URL: https://codereview.chromium.org/935863003
diff --git a/include/gpu/GrResourceKey.h b/include/gpu/GrResourceKey.h
index 906bc6a..1eb7d1f 100644
--- a/include/gpu/GrResourceKey.h
+++ b/include/gpu/GrResourceKey.h
@@ -131,7 +131,7 @@
     friend class TestResource; // For unit test to access kMetaDataCnt.
 
     // bmp textures require 4 uint32_t values.
-    SkAutoSTArray<kMetaDataCnt + 4, uint32_t> fKey;
+    SkAutoSTMalloc<kMetaDataCnt + 4, uint32_t> fKey;
 };
 
 /**