Move instanced index buffer creation to flush time

gm/convexpolyeffect.cpp

Index: gm/convexpolyeffect.cpp
diff --git a/gm/convexpolyeffect.cpp b/gm/convexpolyeffect.cpp
index 07d5fc2112f15a6bcf0f6d945f00ee0e865d3a9e..60b73c571d97a067d5b566d2ed0b88570dd65212 100644
--- a/gm/convexpolyeffect.cpp
+++ b/gm/convexpolyeffect.cpp
@@ -17,6 +17,7 @@
 #include "GrContext.h"
 #include "GrDefaultGeoProcFactory.h"
 #include "GrPathUtils.h"
+#include "GrResourceProvider.h"
 #include "GrTest.h"
 #include "GrTestBatch.h"
 #include "SkColorPriv.h"
@@ -52,8 +53,10 @@ private:
     }
 
     void onGenerateGeometry(GrBatchTarget* batchTarget, const GrPipeline* pipeline) override {
-        size_t vertexStride = this->geometryProcessor()->getVertexStride();
+        SkAutoTUnref<const GrIndexBuffer> indexBuffer(
+            batchTarget->resourceProvider()->refQuadIndexBuffer());
 
+        size_t vertexStride = this->geometryProcessor()->getVertexStride();
         const GrVertexBuffer* vertexBuffer;
         int firstVertex;
 
@@ -62,7 +65,7 @@ private:
                                                               &vertexBuffer,
                                                               &firstVertex);
 
-        if (!vertices || !batchTarget->quadIndexBuffer()) {
+        if (!vertices || !indexBuffer) {
             SkDebugf("Could not allocate buffers\n");
             return;
         }
@@ -82,7 +85,7 @@ private:
         drawInfo.setVertexCount(kVertsPerCubic);
         drawInfo.setStartIndex(0);
         drawInfo.setIndexCount(kIndicesPerCubic);
-        drawInfo.setIndexBuffer(batchTarget->quadIndexBuffer());
+        drawInfo.setIndexBuffer(indexBuffer);
         batchTarget->draw(drawInfo);
     }