Update CaptureAndReplay.md and Python script with links

doc/CaptureAndReplay.md

@@ -170,10 +170,20 @@ as the GLES driver for your application.
 ## Testing
 
 ### Regression Testing Architecture
-The python script uses the job queue pattern. There are n processes running asynchronously and independently, one on each CPU core. Whenever a process (except for the main process) finishes a job and becomes available, it grabs the next job from a shared job queue and runs that job on its CPU core. They keep doing this until there is no more job in the shared job queue. The main process, after filling up the shared job queue and spawning the (n-1) subprocesses that run on the remaining (n-1) CPU cores, waits until all the subprocesses are finished. It then reports the results and cleans up.
+The [python script][link_to_python_script] uses the job queue pattern. We spawn n-1 independent
+worker processes, where n is the value returned by multiprocessing.cpu_count(). Whenever a worker
+process finishes a job and becomes available, it grabs the next job from a shared job queue and
+runs that job on its CPU core. When there are no more jobs in the queue, the worker processes
+terminate and the main process reports results.
 
-![Point-in-time snapshot of the job queue](https://screenshot.googleplex.com/w2QY5ui5FMg.png)
+![Point-in-time snapshot of the job queue](img/RegressionTestingArchitecture.png)
 
 ### Job unit
-A job unit is a test batch. Each test has to go through 3 stages: capture run, replay build, and replay run. The test batch batches the replay build stage of multiple tests together, and the replay run stage of multiple tests together.
-![A test batch as a job unit](https://screenshot.googleplex.com/A4w8ogsnfLw.png)
+A job unit is a test batch. Each test has to go through 3 stages: capture run, replay build, and
+replay run. The test batch batches the replay build stage of multiple tests together, and the
+replay run stage of multiple tests together.
+
+![A test batch as a job unit](img/JobUnit.png)
+
+[link_to_python_script]:https://chromium.googlesource.com/angle/angle/+/refs/heads/master/src/tests/capture_replay_tests.py
+

src/tests/capture_replay_tests.py

@@ -230,6 +230,8 @@ def SetCWDToAngleFolder():
     return cwd
 
 
+# RunTest gets run on each spawned subprocess.
+# See https://chromium.googlesource.com/angle/angle/+/refs/heads/master/doc/CaptureAndReplay.md#testing for architecture
 def RunTest(job_queue, gn_path, autoninja_path, capture_build_dir, replay_build_dir, test_exec,
             replay_exec, trace_dir, result_list):
     trace_folder_path = os.path.join(REPLAY_SAMPLE_FOLDER, trace_dir)
@@ -243,12 +245,14 @@ def RunTest(job_queue, gn_path, autoninja_path, capture_build_dir, replay_build_
             test = job_queue.get()
             print("Running " + test.full_test_name)
             sys.stdout.flush()
+            # stage 1 from the diagram linked above: capture run
             returncode, output = test.Run(test_exec_path, trace_folder_path)
             if returncode != 0 or not CanRunReplay(trace_folder_path):
                 result_list.append((test.full_test_name, "Skipped",
                 "Skipping replay since capture didn't produce appropriate files or has crashed. " \
                 + "Error message: " + output))
                 continue
+            # stage 2 from the diagram linked above: replay build
             returncode, output = test.BuildReplay(gn_path, autoninja_path, replay_build_dir,
                                                   trace_dir, replay_exec)
             if returncode != 0:
@@ -256,6 +260,7 @@ def RunTest(job_queue, gn_path, autoninja_path, capture_build_dir, replay_build_
                     (test.full_test_name, "Skipped",
                      "Skipping replay since failing to build replay. Error message: " + output))
                 continue
+            # stage 2 from the diagram linked above: replay run
             returncode, output = test.RunReplay(replay_exec_path)
             if returncode != 0:
                 result_list.append((test.full_test_name, "Failed", output))