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/gl/FramebufferGL.cpp b/src/libANGLE/renderer/gl/FramebufferGL.cpp
index 620de74..b1065fa 100644
--- a/src/libANGLE/renderer/gl/FramebufferGL.cpp
+++ b/src/libANGLE/renderer/gl/FramebufferGL.cpp
@@ -430,7 +430,8 @@
     }
 
     PixelPackState packState     = context->getGLState().getPackState();
-    const gl::Buffer *packBuffer = context->getGLState().getTargetBuffer(GL_PIXEL_PACK_BUFFER);
+    const gl::Buffer *packBuffer =
+        context->getGLState().getTargetBuffer(gl::BufferBinding::PixelPack);
 
     nativegl::ReadPixelsFormat readPixelsFormat =
         nativegl::GetReadPixelsFormat(mFunctions, mWorkarounds, format, type);