blueslip: Add measure_time wrapper.

Now when we want to measure how long a block
of code takes to execute, we just wrap it with
`blueslip.measure_time`, instead of the awkward
idiom from my original commit of getting a callback
function.

My rationale for the original scheme was that I
wanted to minimize diffs and avoid changing
`const` to `let` in a few cases, but I believe
now that the function wrapper is nicer.

In a few cases I just removed the blueslip timing
code, since I was able to confirm on czo that
the times were pretty minimal.

frontend_tests/zjsunit/zblueslip.js

@@ -119,7 +119,9 @@ exports.make_zblueslip = function () {
         return ex.message;
     };
 
-    lib.start_timing = () => () => {};
+    lib.measure_time = (label, f) => {
+        f();
+    };
 
     lib.preview_node = (node) => "node:" + node;
 

static/js/activity.js

@@ -112,11 +112,9 @@ exports.build_user_sidebar = function () {
 
     const user_ids = buddy_data.get_filtered_and_sorted_user_ids(filter_text);
 
-    const finish = blueslip.start_timing("buddy_list.populate");
-    buddy_list.populate({
-        keys: user_ids,
+    blueslip.measure_time("buddy_list.populate", () => {
+        buddy_list.populate({keys: user_ids});
     });
-    finish();
 
     return user_ids; // for testing
 };

static/js/blueslip.js

@@ -251,14 +251,12 @@ exports.error = function blueslip_error(msg, more_info, stack) {
 
 exports.timings = new Map();
 
-exports.start_timing = function (label) {
+exports.measure_time = function (label, f) {
     const t1 = performance.now();
-
-    return function () {
-        const t2 = performance.now();
-        const elapsed = t2 - t1;
-        exports.timings.set(label, elapsed);
-    };
+    f();
+    const t2 = performance.now();
+    const elapsed = t2 - t1;
+    exports.timings.set(label, elapsed);
 };
 
 // Produces an easy-to-read preview on an HTML element.  Currently

static/js/list_widget.js

@@ -186,7 +186,6 @@ exports.create = function ($container, list, opts) {
 
         const slice = meta.filtered_list.slice(meta.offset, meta.offset + load_count);
 
-        const finish = blueslip.start_timing("ListWidget " + opts.name);
         let html = "";
         for (const item of slice) {
             const s = opts.modifier(item);
@@ -202,8 +201,6 @@ exports.create = function ($container, list, opts) {
             }
         }
 
-        finish();
-
         $container.append($(html));
         meta.offset += load_count;
     };

static/js/pm_list.js

@@ -106,10 +106,8 @@ exports._get_convos = function () {
 };
 
 exports._build_private_messages_list = function () {
-    const finish = blueslip.start_timing("render pm list");
     const convos = exports._get_convos();
     const dom_ast = pm_list_dom.pm_ul(convos);
-    finish();
     return dom_ast;
 };
 

static/js/stream_create.js

@@ -257,16 +257,18 @@ exports.show_new_stream_modal = function () {
     $("#stream-creation").removeClass("hide");
     $(".right .settings").hide();
 
-    const finish = blueslip.start_timing("render new stream users");
-    const all_users = people.get_people_for_stream_create();
-    // Add current user on top of list
-    all_users.unshift(people.get_by_user_id(page_params.user_id));
-    const html = render_new_stream_users({
-        users: all_users,
-        streams: stream_data.get_streams_for_settings_page(),
-        is_admin: page_params.is_admin,
+    let html;
+
+    blueslip.measure_time("render new stream users", () => {
+        const all_users = people.get_people_for_stream_create();
+        // Add current user on top of list
+        all_users.unshift(people.get_by_user_id(page_params.user_id));
+        html = render_new_stream_users({
+            users: all_users,
+            streams: stream_data.get_streams_for_settings_page(),
+            is_admin: page_params.is_admin,
+        });
     });
-    finish();
 
     const container = $("#people_to_add");
     container.html(html);

static/js/stream_list.js

@@ -314,9 +314,8 @@ function set_stream_unread_count(stream_id, count) {
 }
 
 exports.update_streams_sidebar = function (force_rerender) {
-    const finish = blueslip.start_timing("build_stream_list");
     exports.build_stream_list(force_rerender);
-    finish();
+
     exports.stream_cursor.redraw();
 
     if (!narrow_state.active()) {

static/js/subs.js

@@ -400,15 +400,16 @@ function get_stream_id_buckets(stream_ids, query) {
 }
 
 exports.populate_stream_settings_left_panel = function () {
-    const finish = blueslip.start_timing("render left panel");
-    const sub_rows = stream_data.get_updated_unsorted_subs();
+    let html;
+    blueslip.measure_time("render left panel", () => {
+        const sub_rows = stream_data.get_updated_unsorted_subs();
 
-    const template_data = {
-        subscriptions: sub_rows,
-    };
+        const template_data = {
+            subscriptions: sub_rows,
+        };
 
-    const html = render_subscriptions(template_data);
-    finish();
+        html = render_subscriptions(template_data);
+    });
 
     ui.get_content_element($("#subscriptions_table .streams-list")).html(html);
 };

static/js/ui_init.js

@@ -482,7 +482,7 @@ exports.initialize_everything = function () {
 };
 
 $(() => {
-    const finish = blueslip.start_timing("initialize_everything");
-    exports.initialize_everything();
-    finish();
+    blueslip.measure_time("initialize_everything", () => {
+        exports.initialize_everything();
+    });
 });