Fix dav1d Windows msvc build.

      out/Default third_party/dav1d" can build. W/o
      this change, it fails.

Test: set "is_clang=false" in BUILd.gn and "ninja -C
Change-Id: I181ec0f621b0e562e26ae7a580689ff1887605db
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1638883Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Commit-Queue: Haoming Chen <hmchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#666405}

third_party/dav1d/BUILD.gn

@@ -91,6 +91,9 @@ config("dav1d_config") {
     "libdav1d/include/dav1d",
     platform_config_root,
   ]
+  if (is_win && !is_clang) {
+    include_dirs += [ "libdav1d/include/compat/msvc" ]
+  }
 }
 
 dav1d_copts = [
@@ -98,7 +101,11 @@ dav1d_copts = [
   "-D_POSIX_C_SOURCE=200112L",
 ]
 
-if (!is_win) {
+if (is_win) {
+  if (!is_clang) {
+    dav1d_copts += [ "/wd4028" ]
+  }
+} else {
   dav1d_copts += [ "-std=c99" ]
   if (needs_stack_alignment) {
     dav1d_copts += [ stackalign_flag ]