Introduce GrBatch subclasses GrDrawBatch and GrVertexBatch to prepare for non-drawing batches

src/gpu/batches/GrDrawVerticesBatch.cpp

Index: src/gpu/batches/GrDrawVerticesBatch.cpp
diff --git a/src/gpu/batches/GrDrawVerticesBatch.cpp b/src/gpu/batches/GrDrawVerticesBatch.cpp
index f36c54b067f1d18f14de02cb164e294ba7f9eaf6..ebfda362960433288fd7ff8e67d0b7ad64899175 100644
--- a/src/gpu/batches/GrDrawVerticesBatch.cpp
+++ b/src/gpu/batches/GrDrawVerticesBatch.cpp
@@ -184,13 +184,13 @@ void GrDrawVerticesBatch::generateGeometry(GrBatchTarget* batchTarget) {
 }
 
 bool GrDrawVerticesBatch::onCombineIfPossible(GrBatch* t, const GrCaps& caps) {
-    if (!GrPipeline::CanCombine(*this->pipeline(), this->bounds(), *t->pipeline(), t->bounds(),
-                                caps)) {
+    GrDrawVerticesBatch* that = t->cast<GrDrawVerticesBatch>();
+
+    if (!GrPipeline::CanCombine(*this->pipeline(), this->bounds(), *that->pipeline(),
+                                that->bounds(), caps)) {
         return false;
     }
 
-    GrDrawVerticesBatch* that = t->cast<GrDrawVerticesBatch>();
-
     if (!this->batchablePrimitiveType() || this->primitiveType() != that->primitiveType()) {
         return false;
     }
@@ -295,7 +295,7 @@ static void randomize_params(size_t count, size_t maxVertex, SkScalar min, SkSca
     }
 }
 
-BATCH_TEST_DEFINE(VerticesBatch) {
+DRAW_BATCH_TEST_DEFINE(VerticesBatch) {
     GrPrimitiveType type = GrPrimitiveType(random->nextULessThan(kLast_GrPrimitiveType + 1));
     uint32_t primitiveCount = random->nextRangeU(1, 100);