--- a/toolkit/components/telemetry/tests/gtest/TelemetryTestHelpers.cpp
+++ b/toolkit/components/telemetry/tests/gtest/TelemetryTestHelpers.cpp
@@ -171,18 +171,18 @@ GetElement(JSContext* cx, uint32_t index
   valueOut.set(element);
 }
 
 void
 GetSnapshots(JSContext* cx, nsCOMPtr<nsITelemetry> mTelemetry,
              const char* name, JS::MutableHandleValue valueOut, bool is_keyed)
 {
   JS::RootedValue snapshots(cx);
-  nsresult rv = is_keyed ? mTelemetry->SnapshotKeyedHistograms(nsITelemetry::DATASET_RELEASE_CHANNEL_OPTIN, false, false, cx, &snapshots)
-                         : mTelemetry->SnapshotHistograms(nsITelemetry::DATASET_RELEASE_CHANNEL_OPTIN, false, false, cx, &snapshots);
+  nsresult rv = is_keyed ? mTelemetry->SnapshotKeyedHistograms(nsITelemetry::DATASET_RELEASE_CHANNEL_OPTIN, false, cx, &snapshots)
+                         : mTelemetry->SnapshotHistograms(nsITelemetry::DATASET_RELEASE_CHANNEL_OPTIN, false, cx, &snapshots);
 
   JS::RootedValue snapshot(cx);
   GetProperty(cx, "parent", snapshots, &snapshot);
 
   ASSERT_EQ(rv, NS_OK) << "Cannot call histogram snapshots";
   valueOut.set(snapshot);
 }
 

--- a/toolkit/components/telemetry/tests/unit/test_TelemetryHistograms.js
+++ b/toolkit/components/telemetry/tests/unit/test_TelemetryHistograms.js
@@ -68,17 +68,16 @@ function check_histogram(histogram_type,
   // verify properties
   Assert.equal(sum, s.sum);
 
   // there should be exactly one element per bucket
   for (let i of s.counts) {
     Assert.equal(i, 1);
   }
   var hgrams = Telemetry.snapshotHistograms(Ci.nsITelemetry.DATASET_RELEASE_CHANNEL_OPTIN,
-                                            false,
                                             false).parent;
   let gh = hgrams[name];
   Assert.equal(gh.histogram_type, histogram_type);
 
   Assert.equal(gh.min, min);
   Assert.equal(gh.max, max);
 
   // Check that booleans work with nonboolean histograms
@@ -112,17 +111,16 @@ function test_instantiate() {
   let h = Telemetry.getHistogramById(ID);
 
   // Instantiate the subsession histogram through |add| and make sure they match.
   // This MUST be the first use of "TELEMETRY_TEST_COUNT" in this file, otherwise
   // |add| will not instantiate the histogram.
   h.add(1);
   let snapshot = h.snapshot();
   let subsession = Telemetry.snapshotHistograms(Ci.nsITelemetry.DATASET_RELEASE_CHANNEL_OPTIN,
-                                                true /* subsession */,
                                                 false /* clear */).parent;
   Assert.ok(ID in subsession);
   Assert.equal(snapshot.sum, subsession[ID].sum,
                "Histogram and subsession histogram sum must match.");
   // Clear the histogram, so we don't void the assumptions from the other tests.
   h.clear();
 });
 
@@ -172,17 +170,16 @@ add_task(async function test_parameterCo
   }
 });
 
 add_task(async function test_noSerialization() {
   // Instantiate the storage for this histogram and make sure it doesn't
   // get reflected into JS, as it has no interesting data in it.
   Telemetry.getHistogramById("NEWTAB_PAGE_PINNED_SITES_COUNT");
   let histograms = Telemetry.snapshotHistograms(Ci.nsITelemetry.DATASET_RELEASE_CHANNEL_OPTIN,
-                                                false /* subsession */,
                                                 false /* clear */).parent;
   Assert.equal(false, "NEWTAB_PAGE_PINNED_SITES_COUNT" in histograms);
 });
 
 add_task(async function test_boolean_histogram() {
   var h = Telemetry.getHistogramById("TELEMETRY_TEST_BOOLEAN");
   var r = h.snapshot().ranges;
   // boolean histograms ignore numeric parameters
@@ -441,26 +438,24 @@ add_task(async function test_histogramRe
 add_task(async function test_expired_histogram() {
   var test_expired_id = "TELEMETRY_TEST_EXPIRED";
   var dummy = Telemetry.getHistogramById(test_expired_id);
 
   dummy.add(1);
 
   for (let process of ["main", "content", "gpu", "extension"]) {
     let histograms = Telemetry.snapshotHistograms(Ci.nsITelemetry.DATASET_RELEASE_CHANNEL_OPTIN,
-                                                  false /* subsession */,
                                                   false /* clear */);
     if (!(process in histograms)) {
       info("Nothing present for process " + process);
       continue;
     }
     Assert.equal(histograms[process].__expired__, undefined);
   }
   let parentHgrams = Telemetry.snapshotHistograms(Ci.nsITelemetry.DATASET_RELEASE_CHANNEL_OPTIN,
-                                                  false /* subsession */,
                                                   false /* clear */).parent;
   Assert.equal(parentHgrams[test_expired_id], undefined);
 });
 
 add_task(async function test_keyed_histogram() {
   // Check that invalid names get rejected.
 
   let threw = false;
@@ -509,17 +504,16 @@ add_task(async function test_keyed_boole
   testKeys.push(key);
   testSnapShot[key] = testHistograms[2];
   testSnapShot[key].sum = 0;
   testSnapShot[key].counts = [1, 0, 0];
   Assert.deepEqual(h.keys().sort(), testKeys);
   Assert.deepEqual(h.snapshot(), testSnapShot);
 
   let parentHgrams = Telemetry.snapshotKeyedHistograms(Ci.nsITelemetry.DATASET_RELEASE_CHANNEL_OPTIN,
-                                                       false /* subsession */,
                                                        false /* clear */).parent;
   Assert.deepEqual(parentHgrams[KEYED_ID], testSnapShot);
 
   h.clear();
   Assert.deepEqual(h.keys(), []);
   Assert.deepEqual(h.snapshot(), {});
 });
 
@@ -567,17 +561,16 @@ add_task(async function test_keyed_count
   testHistograms[4].counts[0] = 1;
   testHistograms[4].sum = 1;
   testSnapShot[key] = testHistograms[4];
 
   Assert.deepEqual(h.keys().sort(), testKeys);
   Assert.deepEqual(h.snapshot(), testSnapShot);
 
   let parentHgrams = Telemetry.snapshotKeyedHistograms(Ci.nsITelemetry.DATASET_RELEASE_CHANNEL_OPTIN,
-                                                       false /* subsession */,
                                                        false /* clear */).parent;
   Assert.deepEqual(parentHgrams[KEYED_ID], testSnapShot);
 
   // Test clearing categorical histogram.
   h.clear();
   Assert.deepEqual(h.keys(), []);
   Assert.deepEqual(h.snapshot(), {});
 
@@ -642,17 +635,16 @@ add_task(async function test_keyed_flag_
     "ranges": [0, 1, 2],
     "counts": [0, 1, 0]
   };
 
   Assert.deepEqual(h.keys().sort(), [KEY]);
   Assert.deepEqual(h.snapshot(), testSnapshot);
 
   let parentHgrams = Telemetry.snapshotKeyedHistograms(Ci.nsITelemetry.DATASET_RELEASE_CHANNEL_OPTIN,
-                                                       false /* subsession */,
                                                        false /* clear */).parent;
   Assert.deepEqual(parentHgrams[KEYED_ID], testSnapshot);
 
   h.clear();
   Assert.deepEqual(h.keys(), []);
   Assert.deepEqual(h.snapshot(), {});
 });
 
@@ -794,52 +786,47 @@ add_task(async function test_keyed_histo
 });
 
 add_task(async function test_histogramSnapshots() {
   let keyed = Telemetry.getKeyedHistogramById("TELEMETRY_TEST_KEYED_COUNT");
   keyed.add("a", 1);
 
   // Check that keyed histograms are not returned
   let parentHgrams = Telemetry.snapshotHistograms(Ci.nsITelemetry.DATASET_RELEASE_CHANNEL_OPTIN,
-                                                  false /* subsession */,
                                                   false /* clear */).parent;
   Assert.ok(!("TELEMETRY_TEST_KEYED_COUNT" in parentHgrams));
 });
 
 add_task(async function test_datasets() {
   // Check that datasets work as expected.
 
   const RELEASE_CHANNEL_OPTOUT = Ci.nsITelemetry.DATASET_RELEASE_CHANNEL_OPTOUT;
   const RELEASE_CHANNEL_OPTIN  = Ci.nsITelemetry.DATASET_RELEASE_CHANNEL_OPTIN;
 
   // Check that registeredHistogram works properly
   let registered = Telemetry.snapshotHistograms(RELEASE_CHANNEL_OPTIN,
-                                                false /* subsession */,
                                                 false /* clear */);
   registered = new Set(Object.keys(registered.parent));
   Assert.ok(registered.has("TELEMETRY_TEST_FLAG"));
   Assert.ok(registered.has("TELEMETRY_TEST_RELEASE_OPTIN"));
   Assert.ok(registered.has("TELEMETRY_TEST_RELEASE_OPTOUT"));
   registered = Telemetry.snapshotHistograms(RELEASE_CHANNEL_OPTOUT,
-                                            false /* subsession */,
                                             false /* clear */);
   registered = new Set(Object.keys(registered.parent));
   Assert.ok(!registered.has("TELEMETRY_TEST_FLAG"));
   Assert.ok(!registered.has("TELEMETRY_TEST_RELEASE_OPTIN"));
   Assert.ok(registered.has("TELEMETRY_TEST_RELEASE_OPTOUT"));
 
   // Check that registeredKeyedHistograms works properly
   registered = Telemetry.snapshotKeyedHistograms(RELEASE_CHANNEL_OPTIN,
-                                                 false /* subsession */,
                                                  false /* clear */);
   registered = new Set(Object.keys(registered.parent));
   Assert.ok(registered.has("TELEMETRY_TEST_KEYED_FLAG"));
   Assert.ok(registered.has("TELEMETRY_TEST_KEYED_RELEASE_OPTOUT"));
   registered = Telemetry.snapshotKeyedHistograms(RELEASE_CHANNEL_OPTOUT,
-                                                 false /* subsession */,
                                                  false /* clear */);
   registered = new Set(Object.keys(registered.parent));
   Assert.ok(!registered.has("TELEMETRY_TEST_KEYED_FLAG"));
   Assert.ok(registered.has("TELEMETRY_TEST_KEYED_RELEASE_OPTOUT"));
 });
 
 add_task({
   skip_if: () => gIsAndroid
@@ -1171,17 +1158,16 @@ async function test_platformSpecificHist
   mobile_histo.clear();
 
   default_histo.add(42);
   desktop_histo.add(42);
   multiplatform_histo.add(42);
   mobile_histo.add(42);
 
   let histograms = Telemetry.snapshotHistograms(Ci.nsITelemetry.DATASET_RELEASE_CHANNEL_OPTIN,
-                                                false /* subsession */,
                                                 false /* clear */).parent;
 
   Assert.ok(DEFAULT_PLATFORMS_HISTOGRAM in histograms, "Should have recorded default platforms histogram");
   Assert.ok(DESKTOP_ONLY_HISTOGRAM in histograms, "Should have recorded desktop-only histogram");
   Assert.ok(MULTIPLATFORM_HISTOGRAM in histograms, "Should have recorded multiplatform histogram");
 
   Assert.ok(!(MOBILE_ONLY_HISTOGRAM in histograms), "Should not have recorded mobile-only histogram");
 });
@@ -1205,17 +1191,16 @@ async function test_mobileSpecificHistog
   mobile_histo.clear();
 
   default_histo.add(1);
   desktop_histo.add(1);
   multiplatform_histo.add(1);
   mobile_histo.add(1);
 
   let histograms = Telemetry.snapshotHistograms(Ci.nsITelemetry.DATASET_RELEASE_CHANNEL_OPTIN,
-                                                false /* subsession */,
                                                 false /* clear */).parent;
 
   Assert.ok(DEFAULT_PLATFORMS_HISTOGRAM in histograms, "Should have recorded default platforms histogram");
   Assert.ok(MOBILE_ONLY_HISTOGRAM in histograms, "Should have recorded mobile-only histogram");
   Assert.ok(MULTIPLATFORM_HISTOGRAM in histograms, "Should have recorded multiplatform histogram");
 
   Assert.ok(!(DESKTOP_ONLY_HISTOGRAM in histograms), "Should not have recorded desktop-only histogram");
 });