[WebRTC] Fix -Wunused-but-set-variable warnings in the libwebrtc project

https://bugs.webkit.org/show_bug.cgi?id=250622
<rdar://104261631>

Reviewed by Youenn Fablet.

* Source/ThirdParty/libwebrtc/Configurations/Base.xcconfig:
(WK_FIXME_WARNING_CFLAGS):
- Remove -Wno-unused-but-set-variable.
* Source/ThirdParty/libwebrtc/Source/webrtc/common_video/h265/h265_pps_parser.cc:
- Add empty statements for bits_tmp and golomb_ignored
  variables.
* Source/ThirdParty/libwebrtc/Source/webrtc/common_video/h265/h265_sps_parser.cc:
- Add empty statement for golomb_ignored variable.
* Source/ThirdParty/libwebrtc/WebKit/libwebrtc-fix-Wunused-but-set-variable.diff: Add.

Canonical link: https://commits.webkit.org/258956@main

Source/ThirdParty/libwebrtc/Source/webrtc/common_video/h265/h265_pps_parser.cc

@@ -172,6 +172,10 @@ absl::optional<H265PpsParser::PpsState> H265PpsParser::ParseInternal(
   // redundant_pic_cnt_present_flag: u(1)
   pps.redundant_pic_cnt_present_flag = bit_buffer->ReadBits(1);
 
+  // Ignore -Wunused-but-set-variable warnings.
+  (void)bits_tmp;
+  (void)golomb_ignored;
+
   return pps;
 }
 

Source/ThirdParty/libwebrtc/Source/webrtc/common_video/h265/h265_sps_parser.cc

@@ -128,6 +128,7 @@ absl::optional<H265SpsParser::SpsState> H265SpsParser::ParseSpsUpToVui(Bitstream
   }
   // sps_seq_parameter_set_id: ue(v)
   golomb_ignored = buffer->ReadExponentialGolomb();
+  (void)golomb_ignored; // Ignore -Wunused-but-set-variable warning.
   // chrome_format_idc: ue(v)
   chroma_format_idc = buffer->ReadExponentialGolomb();
   if (chroma_format_idc == 3) {

Source/ThirdParty/libwebrtc/WebKit/libwebrtc-fix-Wunused-but-set-variable.diff

@@ -0,0 +1,27 @@
+diff --git a/Source/ThirdParty/libwebrtc/Source/webrtc/common_video/h265/h265_pps_parser.cc b/Source/ThirdParty/libwebrtc/Source/webrtc/common_video/h265/h265_pps_parser.cc
+index 6f13f3b807bb..1df2667d2eae 100644
+--- a/Source/ThirdParty/libwebrtc/Source/webrtc/common_video/h265/h265_pps_parser.cc
++++ b/Source/ThirdParty/libwebrtc/Source/webrtc/common_video/h265/h265_pps_parser.cc
+@@ -172,6 +172,10 @@ absl::optional<H265PpsParser::PpsState> H265PpsParser::ParseInternal(
+   // redundant_pic_cnt_present_flag: u(1)
+   pps.redundant_pic_cnt_present_flag = bit_buffer->ReadBits(1);
+
++  // Ignore -Wunused-but-set-variable warnings.
++  (void)bits_tmp;
++  (void)golomb_ignored;
++
+   return pps;
+ }
+
+diff --git a/Source/ThirdParty/libwebrtc/Source/webrtc/common_video/h265/h265_sps_parser.cc b/Source/ThirdParty/libwebrtc/Source/webrtc/common_video/h265/h265_sps_parser.cc
+index f4628ad63eeb..0d157624f533 100644
+--- a/Source/ThirdParty/libwebrtc/Source/webrtc/common_video/h265/h265_sps_parser.cc
++++ b/Source/ThirdParty/libwebrtc/Source/webrtc/common_video/h265/h265_sps_parser.cc
+@@ -128,6 +128,7 @@ absl::optional<H265SpsParser::SpsState> H265SpsParser::ParseSpsUpToVui(Bitstream
+   }
+   // sps_seq_parameter_set_id: ue(v)
+   golomb_ignored = buffer->ReadExponentialGolomb();
++  (void)golomb_ignored; // Ignore -Wunused-but-set-variable warning.
+   // chrome_format_idc: ue(v)
+   chroma_format_idc = buffer->ReadExponentialGolomb();
+   if (chroma_format_idc == 3) {