Revert of Consolidate GPU buffer implementations

src/gpu/batches/GrAAFillRectBatch.cpp

Index: src/gpu/batches/GrAAFillRectBatch.cpp
diff --git a/src/gpu/batches/GrAAFillRectBatch.cpp b/src/gpu/batches/GrAAFillRectBatch.cpp
index 890a18b57638ef3fb41b6c6b6028139790e00383..9ec8ffdc4a2a46046b4545f612b50e9ab8b5b9ac 100644
--- a/src/gpu/batches/GrAAFillRectBatch.cpp
+++ b/src/gpu/batches/GrAAFillRectBatch.cpp
@@ -28,7 +28,7 @@
 static const int kVertsPerAAFillRect = 8;
 static const int kIndicesPerAAFillRect = 30;
 
-const GrBuffer* get_index_buffer(GrResourceProvider* resourceProvider) {
+const GrIndexBuffer* get_index_buffer(GrResourceProvider* resourceProvider) {
     GR_DEFINE_STATIC_UNIQUE_KEY(gAAFillRectIndexBufferKey);
 
     static const uint16_t gFillAARectIdx[] = {
@@ -191,7 +191,7 @@
         out->setUnknownSingleComponent();
     }
 
-    static const GrBuffer* GetIndexBuffer(GrResourceProvider* rp) {
+    static const GrIndexBuffer* GetIndexBuffer(GrResourceProvider* rp) {
         return get_index_buffer(rp);
     }