Move instanced index buffer creation to flush time

src/gpu/GrBatchTarget.h

Index: src/gpu/GrBatchTarget.h
diff --git a/src/gpu/GrBatchTarget.h b/src/gpu/GrBatchTarget.h
index 9bd6b9409c41c2355e4246e42527e80b5fe1c053..97cd2ed727b9252a24655e7a654f9866e8d2a131 100644
--- a/src/gpu/GrBatchTarget.h
+++ b/src/gpu/GrBatchTarget.h
@@ -121,9 +121,7 @@ public:
     GrVertexBufferAllocPool* vertexPool() { return fVertexPool; }
     GrIndexBufferAllocPool* indexPool() { return fIndexPool; }
 
-    const static int kVertsPerRect = 4;
-    const static int kIndicesPerRect = 6;
-    const GrIndexBuffer* quadIndexBuffer() const { return fGpu->getQuadIndexBuffer(); }
+    GrResourceProvider* resourceProvider() const { return fGpu->getContext()->resourceProvider(); }
 
     // A helper for draws which overallocate and then return data to the pool
     void putBackIndices(size_t indices) { fIndexPool->putBack(indices * sizeof(uint16_t)); }