Send allow_screen_content flag for both key and intra only frames

Cherry-picked from webm/nextgenv2:
https://chromium-review.googlesource.com/#/c/397518/

BUG=webm:1311

Change-Id: I29e7863f40926baddbdcc2b7f2b4d416aa6540cd

av1/decoder/decodeframe.c

diff --git a/av1/decoder/decodeframe.c b/av1/decoder/decodeframe.c
index 2e0887e..fe4eefd 100644
--- a/av1/decoder/decodeframe.c
+++ b/av1/decoder/decodeframe.c
@@ -1854,12 +1854,13 @@
       pbi->need_resync = 0;
     }
 #if CONFIG_PALETTE
-    if (frame_is_intra_only(cm))
-      cm->allow_screen_content_tools = aom_rb_read_bit(rb);
+    cm->allow_screen_content_tools = aom_rb_read_bit(rb);
 #endif  // CONFIG_PALETTE
   } else {
     cm->intra_only = cm->show_frame ? 0 : aom_rb_read_bit(rb);
-
+#if CONFIG_PALETTE
+    if (cm->intra_only) cm->allow_screen_content_tools = aom_rb_read_bit(rb);
+#endif  // CONFIG_PALETTE
     if (cm->error_resilient_mode) {
       cm->reset_frame_context = RESET_FRAME_CONTEXT_ALL;
     } else {

av1/encoder/bitstream.c

diff --git a/av1/encoder/bitstream.c b/av1/encoder/bitstream.c
index 0c6e57a..510c97d 100644
--- a/av1/encoder/bitstream.c
+++ b/av1/encoder/bitstream.c
@@ -2026,12 +2026,13 @@
     write_bitdepth_colorspace_sampling(cm, wb);
     write_frame_size(cm, wb);
 #if CONFIG_PALETTE
-    if (frame_is_intra_only(cm))
-      aom_wb_write_bit(wb, cm->allow_screen_content_tools);
+    aom_wb_write_bit(wb, cm->allow_screen_content_tools);
 #endif  // CONFIG_PALETTE
   } else {
     if (!cm->show_frame) aom_wb_write_bit(wb, cm->intra_only);
-
+#if CONFIG_PALETTE
+    if (cm->intra_only) aom_wb_write_bit(wb, cm->allow_screen_content_tools);
+#endif  // CONFIG_PALETTE
     if (!cm->error_resilient_mode) {
       if (cm->intra_only) {
         aom_wb_write_bit(wb,