Automatically run siso metrics summary for siso builds

siso doesn't generate .ninja_log files so post_build_ninja_summary.py
doesn't work, but it _does_ generate siso_metrics.json files which can
be used to generate similar reports to post_build_ninja_summary.py.

Therefore, when a siso_metrics.json file is detected the siso metrics
summary command is invoked, thus preserving (more or less) the old
behavior.

Bug: b/293657720
Change-Id: I084402ca4dca9895b502ab336fa7b45b770f4768
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/4854377
Reviewed-by: Junji Watanabe <jwata@google.com>
Commit-Queue: Bruce Dawson <brucedawson@chromium.org>

post_build_ninja_summary.py

@@ -54,6 +54,7 @@ import argparse
 import errno
 import fnmatch
 import os
+import subprocess
 import sys
 
 # The number of long build times to report:
@@ -322,6 +323,7 @@ def SummarizeEntries(entries, extra_step_types, elapsed_time_sorting):
 
 def main():
     log_file = '.ninja_log'
+    metrics_file = 'siso_metrics.json'
     parser = argparse.ArgumentParser()
     parser.add_argument('-C', dest='build_directory', help='Build directory.')
     parser.add_argument(
@@ -339,6 +341,7 @@ def main():
     args, _extra_args = parser.parse_known_args()
     if args.build_directory:
         log_file = os.path.join(args.build_directory, log_file)
+        metrics_file = os.path.join(args.build_directory, metrics_file)
     if args.log_file:
         log_file = args.log_file
     if not args.step_types:
@@ -351,6 +354,18 @@ def main():
         global long_ext_count
         long_ext_count += len(args.step_types.split(';'))
 
+    if os.path.exists(metrics_file):
+        # Automatically handle summarizing siso builds.
+        cmd = ['siso.bat' if 'win32' in sys.platform else 'siso']
+        cmd.extend(['metrics', 'summary'])
+        if args.build_directory:
+            cmd.extend(['-C', args.build_directory])
+        if args.step_types:
+            cmd.extend(['--step_types', args.step_types])
+        if args.elapsed_time_sorting:
+            cmd.append('--elapsed_time_sorting')
+        subprocess.run(cmd)
+    else:
         try:
             with open(log_file, 'r') as log:
                 entries = ReadTargets(log, False)