[tools/perf] Fix JavaScript interpolation in action_runner calls

tools/perf/page_sets/repaint_helpers.py

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 from telemetry.page import legacy_page_test
 
 
 def Repaint(action_runner, mode='viewport', width=None, height=None):
   action_runner.WaitForJavaScriptCondition(
     'document.readyState == "complete"', timeout_in_seconds=90)
   # Rasterize only what's visible.
   action_runner.ExecuteJavaScript(
       'chrome.gpuBenchmarking.setRasterizeOnlyVisibleContent();')
 
   args = {}
   args['mode'] = mode
   if width:
     args['width'] = width
   if height:
     args['height'] = height
 
   # Enqueue benchmark
   action_runner.ExecuteJavaScript("""
       window.benchmark_results = {};
       window.benchmark_results.id =
           chrome.gpuBenchmarking.runMicroBenchmark(
               "invalidation_benchmark",
               function(value) {},
-              """ + str(args) + """
+              {{ args }}
           );
-  """)
+      """,
+      args=args)
 
   micro_benchmark_id = action_runner.EvaluateJavaScript(
       'window.benchmark_results.id')
   if not micro_benchmark_id:
     raise legacy_page_test.MeasurementFailure(
         'Failed to schedule invalidation_benchmark.')
 
   with action_runner.CreateInteraction('Repaint'):
     action_runner.RepaintContinuously(seconds=5)
 
-  # TODO(catapult:#3028): Fix interpolation of JavaScript values.
   action_runner.ExecuteJavaScript("""
       window.benchmark_results.message_handled =
           chrome.gpuBenchmarking.sendMessageToMicroBenchmark(
-              """ + str(micro_benchmark_id) + """, {
-                "notify_done": true
-              });
-  """)
+                {{ micro_benchmark_id }}, {
+                  "notify_done": true
+                });
+      """,
+      micro_benchmark_id=micro_benchmark_id)
 
 
 def WaitThenRepaint(action_runner):
   action_runner.Wait(2)
   Repaint(action_runner)