Factor code between PixelUnpackState and PixelPackState

BUG=angleproject:1512

Change-Id: I4c60472d216bfc5198e635d70fd197a5738dde98
Reviewed-on: https://chromium-review.googlesource.com/390133
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/libANGLE/validationES.cpp b/src/libANGLE/validationES.cpp
index 2d3474a..7daa549 100644
--- a/src/libANGLE/validationES.cpp
+++ b/src/libANGLE/validationES.cpp
@@ -1179,7 +1179,7 @@
         const gl::Extents size(width, height, 1);
         const auto &pack = context->getGLState().getPackState();
 
-        auto endByteOrErr = formatInfo.computePackEndByte(type, size, pack);
+        auto endByteOrErr = formatInfo.computePackUnpackEndByte(type, size, pack, false);
         if (endByteOrErr.isError())
         {
             context->handleError(endByteOrErr.getError());
@@ -1230,7 +1230,7 @@
     const gl::Extents size(width, height, 1);
     const auto &pack = context->getGLState().getPackState();
 
-    auto endByteOrErr = formatInfo.computePackEndByte(type, size, pack);
+    auto endByteOrErr = formatInfo.computePackUnpackEndByte(type, size, pack, false);
     if (endByteOrErr.isError())
     {
         context->handleError(endByteOrErr.getError());