Fix x64 visual studio build errors

Bug: angleproject:2740

Change-Id: I44fd2a1daf3dca764e2eef73e437feb32b36dbaa
Reviewed-on: https://chromium-review.googlesource.com/1185234
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
diff --git a/src/tests/test_utils/MultiviewTest.cpp b/src/tests/test_utils/MultiviewTest.cpp
index 79f6475..4ec4064 100644
--- a/src/tests/test_utils/MultiviewTest.cpp
+++ b/src/tests/test_utils/MultiviewTest.cpp
@@ -150,9 +150,9 @@
             }
             for (size_t i = 0; i < colorTextures.size(); ++i)
             {
-                glFramebufferTextureMultiviewSideBySideANGLE(target, GL_COLOR_ATTACHMENT0 + i,
-                                                             colorTextures[i], 0, numViews,
-                                                             viewportOffsets.data());
+                GLenum attachment = static_cast<GLenum>(GL_COLOR_ATTACHMENT0 + i);
+                glFramebufferTextureMultiviewSideBySideANGLE(target, attachment, colorTextures[i],
+                                                             0, numViews, viewportOffsets.data());
             }
             if (depthTexture)
             {
@@ -170,8 +170,9 @@
         case GL_FRAMEBUFFER_MULTIVIEW_LAYERED_ANGLE:
             for (size_t i = 0; i < colorTextures.size(); ++i)
             {
-                glFramebufferTextureMultiviewLayeredANGLE(
-                    target, GL_COLOR_ATTACHMENT0 + i, colorTextures[i], 0, baseViewIndex, numViews);
+                GLenum attachment = static_cast<GLenum>(GL_COLOR_ATTACHMENT0 + i);
+                glFramebufferTextureMultiviewLayeredANGLE(target, attachment, colorTextures[i], 0,
+                                                          baseViewIndex, numViews);
             }
             if (depthTexture)
             {