[experiments] Default unique metadata strings to on in OSS, disable tests (#34039)

This is pretty robust and doesn't warrant the level of testing its
getting right now.

bazel/experiments.bzl

@@ -27,7 +27,6 @@ EXPERIMENTS = {
             "core_end2end_test": [
                 "promise_based_client_call",
                 "promise_based_server_call",
-                "unique_metadata_strings",
             ],
             "cpp_end2end_test": [
                 "promise_based_server_call",
@@ -75,7 +74,6 @@ EXPERIMENTS = {
             "core_end2end_test": [
                 "promise_based_client_call",
                 "promise_based_server_call",
-                "unique_metadata_strings",
             ],
             "cpp_end2end_test": [
                 "promise_based_server_call",
@@ -126,7 +124,6 @@ EXPERIMENTS = {
             "core_end2end_test": [
                 "promise_based_client_call",
                 "promise_based_server_call",
-                "unique_metadata_strings",
             ],
             "cpp_end2end_test": [
                 "promise_based_server_call",

src/core/lib/experiments/experiments.cc

@@ -153,7 +153,7 @@ const ExperimentMetadata g_experiment_metadata[] = {
     {"server_privacy", description_server_privacy,
      additional_constraints_server_privacy, false, false},
     {"unique_metadata_strings", description_unique_metadata_strings,
-     additional_constraints_unique_metadata_strings, false, true},
+     additional_constraints_unique_metadata_strings, true, true},
     {"keepalive_fix", description_keepalive_fix,
      additional_constraints_keepalive_fix, false, false},
     {"keepalive_server_fix", description_keepalive_server_fix,
@@ -295,7 +295,7 @@ const ExperimentMetadata g_experiment_metadata[] = {
     {"server_privacy", description_server_privacy,
      additional_constraints_server_privacy, false, false},
     {"unique_metadata_strings", description_unique_metadata_strings,
-     additional_constraints_unique_metadata_strings, false, true},
+     additional_constraints_unique_metadata_strings, true, true},
     {"keepalive_fix", description_keepalive_fix,
      additional_constraints_keepalive_fix, false, false},
     {"keepalive_server_fix", description_keepalive_server_fix,
@@ -437,7 +437,7 @@ const ExperimentMetadata g_experiment_metadata[] = {
     {"server_privacy", description_server_privacy,
      additional_constraints_server_privacy, false, false},
     {"unique_metadata_strings", description_unique_metadata_strings,
-     additional_constraints_unique_metadata_strings, false, true},
+     additional_constraints_unique_metadata_strings, true, true},
     {"keepalive_fix", description_keepalive_fix,
      additional_constraints_keepalive_fix, false, false},
     {"keepalive_server_fix", description_keepalive_server_fix,

src/core/lib/experiments/experiments.h

@@ -88,7 +88,8 @@ inline bool IsWorkStealingEnabled() {
 inline bool IsClientPrivacyEnabled() { return false; }
 inline bool IsCanaryClientPrivacyEnabled() { return false; }
 inline bool IsServerPrivacyEnabled() { return false; }
-inline bool IsUniqueMetadataStringsEnabled() { return false; }
+#define GRPC_EXPERIMENT_IS_INCLUDED_UNIQUE_METADATA_STRINGS
+inline bool IsUniqueMetadataStringsEnabled() { return true; }
 inline bool IsKeepaliveFixEnabled() { return false; }
 inline bool IsKeepaliveServerFixEnabled() { return false; }
 
@@ -122,7 +123,8 @@ inline bool IsWorkStealingEnabled() {
 inline bool IsClientPrivacyEnabled() { return false; }
 inline bool IsCanaryClientPrivacyEnabled() { return false; }
 inline bool IsServerPrivacyEnabled() { return false; }
-inline bool IsUniqueMetadataStringsEnabled() { return false; }
+#define GRPC_EXPERIMENT_IS_INCLUDED_UNIQUE_METADATA_STRINGS
+inline bool IsUniqueMetadataStringsEnabled() { return true; }
 inline bool IsKeepaliveFixEnabled() { return false; }
 inline bool IsKeepaliveServerFixEnabled() { return false; }
 
@@ -156,7 +158,8 @@ inline bool IsWorkStealingEnabled() {
 inline bool IsClientPrivacyEnabled() { return false; }
 inline bool IsCanaryClientPrivacyEnabled() { return false; }
 inline bool IsServerPrivacyEnabled() { return false; }
-inline bool IsUniqueMetadataStringsEnabled() { return false; }
+#define GRPC_EXPERIMENT_IS_INCLUDED_UNIQUE_METADATA_STRINGS
+inline bool IsUniqueMetadataStringsEnabled() { return true; }
 inline bool IsKeepaliveFixEnabled() { return false; }
 inline bool IsKeepaliveServerFixEnabled() { return false; }
 #endif

src/core/lib/experiments/experiments.yaml

@@ -156,7 +156,7 @@
     lifetimes to be extended leading to memory bloat.
   expiry: 2023/11/01
   owner: ctiller@google.com
-  test_tags: ["core_end2end_test"]
+  test_tags: []
   allow_in_fuzzing_config: true
 - name: keepalive_fix
   description:

src/core/lib/experiments/rollouts.yaml

@@ -87,7 +87,7 @@
 - name: server_privacy
   default: false
 - name: unique_metadata_strings
-  default: false
+  default: true
 - name: keepalive_fix
   default: false
 - name: keepalive_server_fix