LibVideo: Ensure that syntax element counts don't overflow

Integer overflow could sometimes occur due to counts going above 255,
where the values should instead be clamped at their maximum to avoid
wrapping to 0.

Userland/Libraries/LibVideo/VP9/TreeParser.cpp

@@ -668,80 +668,83 @@ u8 TreeParser::calculate_token_probability(u8 node)
 
 void TreeParser::count_syntax_element(SyntaxElementType type, int value)
 {
+    auto increment = [](u8& count) {
+        count = min(static_cast<u32>(count) + 1, 255);
+    };
     switch (type) {
     case SyntaxElementType::Partition:
-        m_decoder.m_syntax_element_counter->m_counts_partition[m_ctx][value]++;
+        increment(m_decoder.m_syntax_element_counter->m_counts_partition[m_ctx][value]);
         return;
     case SyntaxElementType::IntraMode:
     case SyntaxElementType::SubIntraMode:
-        m_decoder.m_syntax_element_counter->m_counts_intra_mode[m_ctx][value]++;
+        increment(m_decoder.m_syntax_element_counter->m_counts_intra_mode[m_ctx][value]);
         return;
     case SyntaxElementType::UVMode:
-        m_decoder.m_syntax_element_counter->m_counts_uv_mode[m_ctx][value]++;
+        increment(m_decoder.m_syntax_element_counter->m_counts_uv_mode[m_ctx][value]);
         return;
     case SyntaxElementType::Skip:
-        m_decoder.m_syntax_element_counter->m_counts_skip[m_ctx][value]++;
+        increment(m_decoder.m_syntax_element_counter->m_counts_skip[m_ctx][value]);
         return;
     case SyntaxElementType::IsInter:
-        m_decoder.m_syntax_element_counter->m_counts_is_inter[m_ctx][value]++;
+        increment(m_decoder.m_syntax_element_counter->m_counts_is_inter[m_ctx][value]);
         return;
     case SyntaxElementType::CompMode:
-        m_decoder.m_syntax_element_counter->m_counts_comp_mode[m_ctx][value]++;
+        increment(m_decoder.m_syntax_element_counter->m_counts_comp_mode[m_ctx][value]);
         return;
     case SyntaxElementType::CompRef:
-        m_decoder.m_syntax_element_counter->m_counts_comp_ref[m_ctx][value]++;
+        increment(m_decoder.m_syntax_element_counter->m_counts_comp_ref[m_ctx][value]);
         return;
     case SyntaxElementType::SingleRefP1:
-        m_decoder.m_syntax_element_counter->m_counts_single_ref[m_ctx][0][value]++;
+        increment(m_decoder.m_syntax_element_counter->m_counts_single_ref[m_ctx][0][value]);
         return;
     case SyntaxElementType::SingleRefP2:
-        m_decoder.m_syntax_element_counter->m_counts_single_ref[m_ctx][1][value]++;
+        increment(m_decoder.m_syntax_element_counter->m_counts_single_ref[m_ctx][1][value]);
         return;
     case SyntaxElementType::MVSign:
-        m_decoder.m_syntax_element_counter->m_counts_mv_sign[m_mv_component][value]++;
+        increment(m_decoder.m_syntax_element_counter->m_counts_mv_sign[m_mv_component][value]);
         return;
     case SyntaxElementType::MVClass0Bit:
-        m_decoder.m_syntax_element_counter->m_counts_mv_class0_bit[m_mv_component][value]++;
+        increment(m_decoder.m_syntax_element_counter->m_counts_mv_class0_bit[m_mv_component][value]);
         return;
     case SyntaxElementType::MVBit:
         VERIFY(m_mv_bit < MV_OFFSET_BITS);
-        m_decoder.m_syntax_element_counter->m_counts_mv_bits[m_mv_component][m_mv_bit][value]++;
+        increment(m_decoder.m_syntax_element_counter->m_counts_mv_bits[m_mv_component][m_mv_bit][value]);
         m_mv_bit = 0xFF;
         return;
     case SyntaxElementType::TXSize:
-        m_decoder.m_syntax_element_counter->m_counts_tx_size[m_decoder.m_max_tx_size][m_ctx][value]++;
+        increment(m_decoder.m_syntax_element_counter->m_counts_tx_size[m_decoder.m_max_tx_size][m_ctx][value]);
         return;
     case SyntaxElementType::InterMode:
-        m_decoder.m_syntax_element_counter->m_counts_inter_mode[m_ctx][value]++;
+        increment(m_decoder.m_syntax_element_counter->m_counts_inter_mode[m_ctx][value]);
         return;
     case SyntaxElementType::InterpFilter:
-        m_decoder.m_syntax_element_counter->m_counts_interp_filter[m_ctx][value]++;
+        increment(m_decoder.m_syntax_element_counter->m_counts_interp_filter[m_ctx][value]);
         return;
     case SyntaxElementType::MVJoint:
-        m_decoder.m_syntax_element_counter->m_counts_mv_joint[value]++;
+        increment(m_decoder.m_syntax_element_counter->m_counts_mv_joint[value]);
         return;
     case SyntaxElementType::MVClass:
-        m_decoder.m_syntax_element_counter->m_counts_mv_class[m_mv_component][value]++;
+        increment(m_decoder.m_syntax_element_counter->m_counts_mv_class[m_mv_component][value]);
         return;
     case SyntaxElementType::MVClass0FR:
         VERIFY(m_mv_class0_bit < CLASS0_SIZE);
-        m_decoder.m_syntax_element_counter->m_counts_mv_class0_fr[m_mv_component][m_mv_class0_bit][value]++;
+        increment(m_decoder.m_syntax_element_counter->m_counts_mv_class0_fr[m_mv_component][m_mv_class0_bit][value]);
         m_mv_class0_bit = 0xFF;
         return;
     case SyntaxElementType::MVClass0HP:
-        m_decoder.m_syntax_element_counter->m_counts_mv_class0_hp[m_mv_component][value]++;
+        increment(m_decoder.m_syntax_element_counter->m_counts_mv_class0_hp[m_mv_component][value]);
         return;
     case SyntaxElementType::MVFR:
-        m_decoder.m_syntax_element_counter->m_counts_mv_fr[m_mv_component][value]++;
+        increment(m_decoder.m_syntax_element_counter->m_counts_mv_fr[m_mv_component][value]);
         return;
     case SyntaxElementType::MVHP:
-        m_decoder.m_syntax_element_counter->m_counts_mv_hp[m_mv_component][value]++;
+        increment(m_decoder.m_syntax_element_counter->m_counts_mv_hp[m_mv_component][value]);
         return;
     case SyntaxElementType::Token:
-        m_decoder.m_syntax_element_counter->m_counts_token[m_tx_size][m_plane > 0][m_decoder.m_is_inter][m_band][m_ctx][min(2, value)]++;
+        increment(m_decoder.m_syntax_element_counter->m_counts_token[m_tx_size][m_plane > 0][m_decoder.m_is_inter][m_band][m_ctx][min(2, value)]);
         return;
     case SyntaxElementType::MoreCoefs:
-        m_decoder.m_syntax_element_counter->m_counts_more_coefs[m_tx_size][m_plane > 0][m_decoder.m_is_inter][m_band][m_ctx][value]++;
+        increment(m_decoder.m_syntax_element_counter->m_counts_more_coefs[m_tx_size][m_plane > 0][m_decoder.m_is_inter][m_band][m_ctx][value]);
         return;
     case SyntaxElementType::DefaultIntraMode:
     case SyntaxElementType::DefaultUVMode: