Remove fIntendedType from GrMtlBuffer. Add accessor to base class

Fixes unused member warning-as-error.

Change-Id: I9468a1b1cb106eeb7818afe87f5cda7eb75910de
Reviewed-on: https://skia-review.googlesource.com/c/189497
Commit-Queue: Brian Salomon <bsalomon@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
Auto-Submit: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
diff --git a/src/gpu/GrBuffer.h b/src/gpu/GrBuffer.h
index 128ec48..d90b587 100644
--- a/src/gpu/GrBuffer.h
+++ b/src/gpu/GrBuffer.h
@@ -102,6 +102,7 @@
 
 protected:
     GrBuffer(GrGpu*, size_t sizeInBytes, GrGpuBufferType, GrAccessPattern);
+    GrGpuBufferType intendedType() const { return fIntendedType; }
 
     void* fMapPtr;