Revert "Default enable WebRTC-HeaderExtensionNegotiateMemory"

This reverts commit 4ecf297a4c0af68ff8af8c3a8e6b0832bddd14d5.

Reason for revert: Impacted unexpected application usages

Original change's description:
> Default enable WebRTC-HeaderExtensionNegotiateMemory
>
> Spec change: https://github.com/w3c/webrtc-extensions/pull/238
>
> Chromestatus entry for change: https://chromestatus.com/feature/5135528638939136
>
> Bug: webrtc:439514253
> Change-Id: I296f2f06dd69b4e30be419b44c926acfd2722e2d
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/407821
> Commit-Queue: Harald Alvestrand <hta@webrtc.org>
> Reviewed-by: Guido Urdaneta <guidou@webrtc.org>
> Cr-Commit-Position: refs/heads/main@{#45993}

(cherry picked from commit 74d988fd57f8f1b6722d8ac6f49c686b9f2bc196)

Bug: webrtc:439514253, chromium:467164231
Change-Id: I95dbc8cbaf1b769ffaea291801684bc26e4b9ccb
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/433102
Reviewed-by: Guido Urdaneta <guidou@webrtc.org>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Cr-Original-Commit-Position: refs/heads/main@{#46456}
No-Try: True
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/433485
Commit-Queue: Guido Urdaneta <guidou@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/branch-heads/7499@{#3}
Cr-Branched-From: 1dfd30cf31a029cd127674a11e65c54c07afaf5d-refs/heads/main@{#46046}

pc/rtp_transceiver.cc

diff --git a/pc/rtp_transceiver.cc b/pc/rtp_transceiver.cc
index b038367..72e6ee2 100644
--- a/pc/rtp_transceiver.cc
+++ b/pc/rtp_transceiver.cc
@@ -869,19 +869,19 @@
   RTC_DCHECK(content);
   if (sdp_type == SdpType::kAnswer || sdp_type == SdpType::kPrAnswer) {
     negotiated_header_extensions_ = content->rtp_header_extensions();
-    if (!env_.field_trials().IsDisabled(
+    if (env_.field_trials().IsEnabled(
             "WebRTC-HeaderExtensionNegotiateMemory")) {
       header_extensions_to_negotiate_ = GetNegotiatedHeaderExtensions();
     }
   } else if (sdp_type == SdpType::kOffer) {
-    if (!env_.field_trials().IsDisabled(
+    if (env_.field_trials().IsEnabled(
             "WebRTC-HeaderExtensionNegotiateMemory")) {
       header_extensions_for_rollback_ = header_extensions_to_negotiate_;
       header_extensions_to_negotiate_ =
           GetOfferedAndImplementedHeaderExtensions(content);
     }
   } else if (sdp_type == SdpType::kRollback) {
-    if (!env_.field_trials().IsDisabled(
+    if (env_.field_trials().IsEnabled(
             "WebRTC-HeaderExtensionNegotiateMemory")) {
       RTC_CHECK(!header_extensions_for_rollback_.empty());
       header_extensions_to_negotiate_ = header_extensions_for_rollback_;

pc/rtp_transmission_manager.cc

diff --git a/pc/rtp_transmission_manager.cc b/pc/rtp_transmission_manager.cc
index 3ca54aa..31f9a76 100644
--- a/pc/rtp_transmission_manager.cc
+++ b/pc/rtp_transmission_manager.cc
@@ -323,8 +323,7 @@
   // could be invalid, but should not cause a crash).
   RTC_DCHECK(!FindSenderById(sender->id()));
   std::vector<RtpHeaderExtensionCapability> header_extensions;
-  if (!env_.field_trials().IsDisabled(
-          "WebRTC-HeaderExtensionNegotiateMemory")) {
+  if (env_.field_trials().IsEnabled("WebRTC-HeaderExtensionNegotiateMemory")) {
     // If we have already negotiated header extensions for this type,
     // reuse the negotiated state for new transceivers of the same type.
     for (const auto& transceiver : transceivers()->List()) {