Fix silly bugs around overscan flag detection.

ui/base/x/x11_util.cc

Index: ui/base/x/x11_util.cc
diff --git a/ui/base/x/x11_util.cc b/ui/base/x/x11_util.cc
index 35e27636d94ecc64277e39bb17b6605d9166882c..5d37b1d8ae9fbee0c76b1c7f00c18deaa0f207a5 100644
--- a/ui/base/x/x11_util.cc
+++ b/ui/base/x/x11_util.cc
@@ -1443,14 +1443,14 @@ bool ParseOutputOverscanFlag(const unsigned char* prop,
           nitems)
         break;
 
-      if (tag != kExtendedTag && payload_length < 2) {
+      if (tag != kExtendedTag || payload_length < 2) {
         data_block += payload_length + 1;
         continue;
       }
 
       unsigned char extended_tag_code = data_block[1];
       if (extended_tag_code != kExtendedVideoCapabilityTag) {
-        data_block += payload_length;
+        data_block += payload_length + 1;
         continue;
       }