Use single alloc for vulkan optimal image heaps to fix memory crash

src/gpu/vk/GrVkGpu.cpp

Index: src/gpu/vk/GrVkGpu.cpp
diff --git a/src/gpu/vk/GrVkGpu.cpp b/src/gpu/vk/GrVkGpu.cpp
index b80835441a540bfb29b15daa1b02ac4a47e976ca..05aa1de152f160518d01fc7e3dc87115c8180e33 100644
--- a/src/gpu/vk/GrVkGpu.cpp
+++ b/src/gpu/vk/GrVkGpu.cpp
@@ -135,7 +135,10 @@ GrVkGpu::GrVkGpu(GrContext* context, const GrContextOptions& options,
 
     // set up our heaps
     fHeaps[kLinearImage_Heap].reset(new GrVkHeap(this, GrVkHeap::kSubAlloc_Strategy, 16*1024*1024));
-    fHeaps[kOptimalImage_Heap].reset(new GrVkHeap(this, GrVkHeap::kSubAlloc_Strategy, 64*1024*1024));
+    // We want the OptimalImage_Heap to use a SubAlloc_strategy but it occasionally causes the
+    // device to run out of memory. Most likely this is caused by fragmentation in the device heap
+    // and we can't allocate more. Until we get a fix moving this to SingleAlloc.
+    fHeaps[kOptimalImage_Heap].reset(new GrVkHeap(this, GrVkHeap::kSingleAlloc_Strategy, 64*1024*1024));
     fHeaps[kSmallOptimalImage_Heap].reset(new GrVkHeap(this, GrVkHeap::kSubAlloc_Strategy, 2*1024*1024));
     fHeaps[kVertexBuffer_Heap].reset(new GrVkHeap(this, GrVkHeap::kSingleAlloc_Strategy, 0));
     fHeaps[kIndexBuffer_Heap].reset(new GrVkHeap(this, GrVkHeap::kSingleAlloc_Strategy, 0));