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

src/gpu/GrBufferedDrawTarget.cpp

Index: src/gpu/GrBufferedDrawTarget.cpp
diff --git a/src/gpu/GrBufferedDrawTarget.cpp b/src/gpu/GrBufferedDrawTarget.cpp
index e33950bf08d4a66d8c2d914708a99b20d1d9b688..36542a1127e93c1c69ddb504c6cb463a228fd709 100644
--- a/src/gpu/GrBufferedDrawTarget.cpp
+++ b/src/gpu/GrBufferedDrawTarget.cpp
@@ -26,7 +26,7 @@ GrBufferedDrawTarget::~GrBufferedDrawTarget() {
     this->reset();
 }
 
-void GrBufferedDrawTarget::onDrawBatch(GrBatch* batch) {
+void GrBufferedDrawTarget::onDrawBatch(GrDrawBatch* batch) {
     fCommands->recordDrawBatch(batch, *this->caps());
 }