[MIPS] Enable swiftshader for mipsel and mips64el

BUG=

Change-Id: I621c411f767d2f1442bc45db78f3562101700c27
Reviewed-on: https://chromium-review.googlesource.com/c/1322870Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606572}

ui/gl/BUILD.gn

@@ -15,7 +15,8 @@ declare_args() {
   enable_swiftshader = (is_win || is_linux || (is_mac && use_egl) ||
                         is_chromeos || is_fuchsia) &&
                        (target_cpu == "x86" || target_cpu == "x64" ||
-                        target_cpu == "arm64")
+                        target_cpu == "arm64" || target_cpu == "mipsel" ||
+                        target_cpu == "mips64el")
 }
 
 use_glx = use_x11 || ozone_platform_x11