Add read support of RtpStreamId/RepairedRtpStreamId header extensions.

webrtc/test/fuzzers/rtp_header_fuzzer.cc

Index: webrtc/test/fuzzers/rtp_header_fuzzer.cc
diff --git a/webrtc/test/fuzzers/rtp_header_fuzzer.cc b/webrtc/test/fuzzers/rtp_header_fuzzer.cc
index 914a8fb9494bc2e701d658ec5c1e55414b6a0586..9e111a80f249337e2d0f93ceb72641031b663310 100644
--- a/webrtc/test/fuzzers/rtp_header_fuzzer.cc
+++ b/webrtc/test/fuzzers/rtp_header_fuzzer.cc
@@ -15,30 +15,31 @@
 #include "webrtc/modules/rtp_rtcp/source/rtp_utility.h"
 
 namespace webrtc {
-// We decide which header extensions to register by reading one byte
+// We decide which header extensions to register by reading two bytes
 // from the beginning of |data| and interpreting it as a bitmask over
-// the RTPExtensionType enum. This assert ensures one byte is enough.
-static_assert(kRtpExtensionNumberOfExtensions <= 8,
+// the RTPExtensionType enum. This assert ensures two bytes are enough.
+static_assert(kRtpExtensionNumberOfExtensions <= 16,
               "Insufficient bits read to configure all header extensions. Add "
               "an extra byte and update the switches.");
 
 void FuzzOneInput(const uint8_t* data, size_t size) {
-  if (size <= 1)
+  if (size <= 2)
     return;
 
   // Don't use the configuration byte as part of the packet.
-  std::bitset<8> extensionMask(data[0]);
-  data++;
-  size--;
+  std::bitset<16> extensionMask(*reinterpret_cast<const uint16_t*>(data));
+  data += 2;
+  size -= 2;
 
   RtpPacketReceived::ExtensionManager extensions;
+  // Skip i = 0 since it maps to ExtensionNone and extension id = 0 is invalid.
   for (int i = 0; i < kRtpExtensionNumberOfExtensions; i++) {
     RTPExtensionType extension_type = static_cast<RTPExtensionType>(i);
     if (extensionMask[i] && extension_type != kRtpExtensionNone) {
       // Extensions are registered with an ID, which you signal to the
       // peer so they know what to expect. This code only cares about
       // parsing so the value of the ID isn't relevant; we use i.
-      extensions.Register(extension_type, i);
+      extensions.RegisterByType(i, extension_type);
     }
   }