Use transfer buffer for BatchAtlas texture copies

src/gpu/gl/GrGLGpu.cpp

Index: src/gpu/gl/GrGLGpu.cpp
diff --git a/src/gpu/gl/GrGLGpu.cpp b/src/gpu/gl/GrGLGpu.cpp
index 4f09ebae00b4556edf52cdb85b6a34d9035277fc..b01310ef8c67a1de1d1e098295a366763e5ed940 100644
--- a/src/gpu/gl/GrGLGpu.cpp
+++ b/src/gpu/gl/GrGLGpu.cpp
@@ -920,12 +920,13 @@ bool GrGLGpu::onTransferPixels(GrSurface* surface,
 
     bool success = false;
     GrMipLevel mipLevel;
-    mipLevel.fPixels = transferBuffer;
+    mipLevel.fPixels = (void*)offset;
     mipLevel.fRowBytes = rowBytes;
     SkSTArray<1, GrMipLevel> texels;
     texels.push_back(mipLevel);
     success = this->uploadTexData(glTex->desc(), glTex->target(), kTransfer_UploadType,
                                   left, top, width, height, config, texels);
+
     if (success) {
         SkIRect rect = SkIRect::MakeXYWH(left, top, width, height);
         this->didWriteToSurface(surface, &rect);
@@ -1196,6 +1197,14 @@ bool GrGLGpu::uploadTexData(const GrSurfaceDesc& desc,
 
     SkASSERT(this->caps()->isConfigTexturable(desc.fConfig));
 
+    // unbind any previous transfer buffer if not transferring
+    auto& xferBufferState = fHWBufferState[kXferCpuToGpu_GrBufferType];
+    if (kTransfer_UploadType != uploadType && 
+        SK_InvalidUniqueID != xferBufferState.fBoundBufferUniqueID) {
+        GL_CALL(BindBuffer(xferBufferState.fGLTarget, 0));
+        xferBufferState.invalidate();
+    }
+
     // texels is const.
     // But we may need to flip the texture vertically to prepare it.
     // Rather than flip in place and alter the incoming data,