Move compute_combined_buffer_size behind GR_TEST_UTILS

Change-Id: I7df21ef7f3b491be5d54477f2429e4ab7603e14b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/213671
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
diff --git a/src/gpu/vk/GrVkGpu.cpp b/src/gpu/vk/GrVkGpu.cpp
index f6309ab..92bd287 100644
--- a/src/gpu/vk/GrVkGpu.cpp
+++ b/src/gpu/vk/GrVkGpu.cpp
@@ -1522,6 +1522,7 @@
     return 0;
 }
 
+#if GR_TEST_UTILS
 static size_t compute_combined_buffer_size(GrPixelConfig config, size_t bpp, int w, int h,
                                            SkTArray<size_t>* individualMipOffsets,
                                            uint32_t mipLevels) {
@@ -1562,7 +1563,6 @@
     return combinedBufferSize;
 }
 
-#if GR_TEST_UTILS
 bool GrVkGpu::createTestingOnlyVkImage(GrPixelConfig config, int w, int h, bool texturable,
                                        bool renderable, GrMipMapped mipMapped, const void* srcData,
                                        size_t srcRowBytes, GrVkImageInfo* info) {