Set up cache in vulkan to reuse GrVkPrograms (aka VkPipelines)

src/gpu/GrStencil.cpp

Index: src/gpu/GrStencil.cpp
diff --git a/src/gpu/GrStencil.cpp b/src/gpu/GrStencil.cpp
index f37aa317ec37b20f9ff0f731278ab27dedc8bf66..9dfe330a5c7af39b530a1732f8bb8a959cc486ee 100644
--- a/src/gpu/GrStencil.cpp
+++ b/src/gpu/GrStencil.cpp
@@ -9,6 +9,8 @@
 
 #include "GrStencil.h"
 
+#include "GrProcessor.h"
+
 ////////////////////////////////////////////////////////////////////////////////
 // Stencil Rules for Merging user stencil space into clip
 
@@ -393,3 +395,10 @@ bool GrStencilSettings::GetClipPasses(
     }
     return false;
 }
+
+void GrStencilSettings::genKey(GrProcessorKeyBuilder* b) const {
+    static const int kCount = sizeof(GrStencilSettings) / sizeof(uint32_t);
+    GR_STATIC_ASSERT(0 == sizeof(GrStencilSettings) % sizeof(uint32_t));
+    uint32_t* key = b->add32n(kCount);
+    memcpy(key, this, sizeof(GrStencilSettings));
+}