Move av1_buildflags from deps to public_deps

"media/base/video_codecs.h" includes
"third_party/libaom/av1_buildflags.h" which is a generated header. This
should be a public_deps since it's included in another header file.

Change-Id: Ie9b340f5866174b0d33ea5289e9ca83aa26db3f8

Bug: 868764
Change-Id: Ie9b340f5866174b0d33ea5289e9ca83aa26db3f8
Reviewed-on: https://chromium-review.googlesource.com/1154528Reviewed-by: Dan Sanders <sandersd@chromium.org>
Commit-Queue: Dale Curtis <dalecurtis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579462}

media/base/BUILD.gn

@@ -294,13 +294,13 @@ jumbo_source_set("base") {
     ":video_facing",
     "//media:media_buildflags",
     "//media:shared_memory_support",
+    "//third_party/libaom:av1_buildflags",
     "//ui/gfx:color_space",
   ]
   deps = [
     "//base/allocator:buildflags",
     "//gpu/command_buffer/common",
     "//skia",
-    "//third_party/libaom:av1_buildflags",
     "//third_party/libyuv",
     "//third_party/widevine/cdm:headers",
     "//ui/display:display",