Fix warning in standalone in new validation.

BUG=angleproject:1512

Change-Id: Ifdb8d4c38e3c90e03eee42ba9fd6390dffd61363
Reviewed-on: https://chromium-review.googlesource.com/388611
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>

BUILD.gn

@@ -55,6 +55,7 @@ config("extra_warnings") {
     cflags = [
       "/we4244",  # Conversion: possible loss of data.
       "/we4456",  # Variable shadowing.
+      "/we4458",  # declaration hides class member.
     ]
   }
 }

src/libANGLE/formatutils.cpp

@@ -960,11 +960,11 @@ gl::ErrorOrResult<GLuint> InternalFormat::computeUnpackSize(
 
     CheckedNumeric<GLuint> depthMinusOne  = size.depth - 1;
     CheckedNumeric<GLuint> heightMinusOne = size.height - 1;
-    CheckedNumeric<GLuint> pixelBytes     = computePixelBytes(formatType);
+    CheckedNumeric<GLuint> bytes          = computePixelBytes(formatType);
 
     CheckedNumeric<GLuint> totalSize = depthMinusOne * depthPitch;
     totalSize += heightMinusOne * rowPitch;
-    totalSize += size.width * pixelBytes;
+    totalSize += size.width * bytes;
 
     ANGLE_TRY_CHECKED_MATH(totalSize);