Use a packed enum for buffer targets.

BUG=angleproject:2169

Change-Id: I4e08973d0e16404b7b8ee2f119e29ac502e28669
Reviewed-on: https://chromium-review.googlesource.com/723865
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
diff --git a/src/libANGLE/renderer/vulkan/FramebufferVk.cpp b/src/libANGLE/renderer/vulkan/FramebufferVk.cpp
index cfa26a6..99530ec 100644
--- a/src/libANGLE/renderer/vulkan/FramebufferVk.cpp
+++ b/src/libANGLE/renderer/vulkan/FramebufferVk.cpp
@@ -327,7 +327,7 @@
     params.format      = format;
     params.type        = type;
     params.outputPitch = inputPitch;
-    params.packBuffer  = glState.getTargetBuffer(GL_PIXEL_UNPACK_BUFFER);
+    params.packBuffer  = glState.getTargetBuffer(gl::BufferBinding::PixelPack);
     params.pack        = glState.getPackState();
 
     PackPixels(params, angleFormat, inputPitch, mapPointer, reinterpret_cast<uint8_t *>(pixels));