[Sync] Reduce sharing message sync latency.

Add switch to fallback to default latency value.

Bug: 1034928
Change-Id: I5b4bf1bb5e3d80ab854b1c6b9758c4c06c26152f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2022765Reviewed-by: vitaliii <vitaliii@chromium.org>
Reviewed-by: Marc Treib <treib@chromium.org>
Commit-Queue: Rushan Suleymanov <rushans@google.com>
Cr-Commit-Position: refs/heads/master@{#735387}

components/sync/base/sync_base_switches.cc

@@ -17,6 +17,12 @@ const base::Feature kSyncForceDisableScryptForCustomPassphrase{
 const base::Feature kSyncE2ELatencyMeasurement = {
     "SyncE2ELatencyMeasurement", base::FEATURE_DISABLED_BY_DEFAULT};
 
+const base::Feature kSyncCustomSharingMessageNudgeDelay = {
+    "SyncCustomSharingMessageNudgeDelay", base::FEATURE_ENABLED_BY_DEFAULT};
+const base::FeatureParam<int> kSyncSharingMessageNudgeDelayMilliseconds{
+    &kSyncCustomSharingMessageNudgeDelay,
+    "SyncSharingMessageNudgeDelayMilliseconds", 50};
+
 const base::Feature kDoNotSyncFaviconDataTypes{
     "DoNotSyncFaviconDataTypes", base::FEATURE_ENABLED_BY_DEFAULT};
 

components/sync/base/sync_base_switches.h

@@ -6,11 +6,14 @@
 #define COMPONENTS_SYNC_BASE_SYNC_BASE_SWITCHES_H_
 
 #include "base/feature_list.h"
+#include "base/metrics/field_trial_params.h"
 
 namespace switches {
 
 extern const base::Feature kSyncForceDisableScryptForCustomPassphrase;
 extern const base::Feature kSyncE2ELatencyMeasurement;
+extern const base::Feature kSyncCustomSharingMessageNudgeDelay;
+extern const base::FeatureParam<int> kSyncSharingMessageNudgeDelayMilliseconds;
 extern const base::Feature kDoNotSyncFaviconDataTypes;
 
 }  // namespace switches

components/sync/engine_impl/cycle/nudge_tracker.cc

@@ -7,6 +7,7 @@
 #include <algorithm>
 #include <utility>
 
+#include "components/sync/base/sync_base_switches.h"
 #include "components/sync/engine/polling_constants.h"
 
 namespace syncer {
@@ -19,6 +20,16 @@ const int kSlowNudgeDelayMilliseconds = 2000;
 const int kSyncRefreshDelayMilliseconds = 500;
 const int kSyncSchedulerDelayMilliseconds = 250;
 
+base::TimeDelta GetSharingMessageDelay(base::TimeDelta default_delay) {
+  if (!base::FeatureList::IsEnabled(
+          switches::kSyncCustomSharingMessageNudgeDelay)) {
+    return default_delay;
+  }
+
+  return base::TimeDelta::FromMilliseconds(
+      switches::kSyncSharingMessageNudgeDelayMilliseconds.Get());
+}
+
 base::TimeDelta GetDefaultDelayForType(ModelType model_type,
                                        base::TimeDelta minimum_delay) {
   switch (model_type) {
@@ -35,6 +46,8 @@ base::TimeDelta GetDefaultDelayForType(ModelType model_type,
       // Types with sometimes automatic changes get longer delays to allow more
       // coalescing.
       return base::TimeDelta::FromMilliseconds(kSlowNudgeDelayMilliseconds);
+    case SHARING_MESSAGE:
+      return GetSharingMessageDelay(minimum_delay);
     default:
       return minimum_delay;
   }

components/sync/engine_impl/cycle/nudge_tracker_unittest.cc

@@ -870,6 +870,9 @@ TEST_F(NudgeTrackerTest, NoTypesShorterThanDefault) {
 
   std::map<ModelType, base::TimeDelta> delay_map;
   ModelTypeSet protocol_types = ProtocolTypes();
+  // Add exception for low-latency data type.
+  protocol_types.Remove(syncer::SHARING_MESSAGE);
+
   for (ModelType type : protocol_types) {
     delay_map[type] = base::TimeDelta();
   }