android: Add debug logs for trace event rewriter

R=martinkong@google.com

Bug: 402434135
Change-Id: I42d09456e8d689d0179fe4dcb3e640189cd96801
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6343733
Reviewed-by: Martin Kong <martinkong@google.com>
Auto-Submit: Peter Wen <wnwen@chromium.org>
Commit-Queue: Martin Kong <martinkong@google.com>
Cr-Commit-Position: refs/heads/main@{#1431024}

build/android/gyp/trace_event_bytecode_rewriter.py

@@ -5,6 +5,7 @@
 """Wrapper script around TraceEventAdder script."""
 
 import argparse
+import logging
 import sys
 import tempfile
 import os
@@ -19,6 +20,7 @@ _MAX_CMDLINE = 10000
 
 
 def main(argv):
+  build_utils.InitLogging('TRACE_EVENT_REWRITER_DEBUG')
   argv = build_utils.ExpandFileArgs(argv[1:])
   parser = argparse.ArgumentParser()
   action_helpers.add_depfile_arg(parser)
@@ -46,12 +48,15 @@ def main(argv):
   ]
   if sum(len(x) for x in cmd) > _MAX_CMDLINE:
     # Cannot put --classpath in the args file because that is consumed by the
-    # wrapper script.
-    args_file = tempfile.NamedTemporaryFile(mode='w')
+    # wrapper script. Keep the args file on disk when debugging.
+    is_debug = logging.getLogger().isEnabledFor(logging.DEBUG)
+    args_file = tempfile.NamedTemporaryFile(mode='w', delete=not is_debug)
     args_file.write('\n'.join(cmd[3:]))
     args_file.flush()
     cmd[3:] = ['@' + args_file.name]
 
+  logging.debug(' '.join(cmd))
+
   build_utils.CheckOutput(cmd, print_stdout=True)
 
   build_utils.Touch(args.stamp)