[code coverage] Add more logs for debugging

Will delete unnecessary logs later.

Bug: 1026891
Change-Id: I56cbd4d73b5805418167c70ff142ce9a4a1e40a3
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1929528Reviewed-by: Yuke Liao <liaoyuke@chromium.org>
Commit-Queue: Yun Liu <yliuyliu@google.com>
Cr-Commit-Position: refs/heads/master@{#718329}

testing/merge_scripts/code_coverage/merge_lib.py

@@ -135,6 +135,7 @@ def _validate_and_convert_profraws(profraw_files, profdata_tool_path):
   counter_overflows = multiprocessing.Manager().list()
 
   for profraw_file in profraw_files:
+    logging.info('Converting profraw file: %r', profraw_file)
     pool.apply_async(
         _validate_and_convert_profraw,
         (profraw_file, output_profdata_files, invalid_profraw_files,
@@ -168,6 +169,7 @@ def _validate_and_convert_profraw(profraw_file, output_profdata_files,
     # Redirecting stderr is required because when error happens, llvm-profdata
     # writes the error output to stderr and our error handling logic relies on
     # that output.
+    logging.info('Converting %r to %r', profraw_file, output_profdata_file)
     validation_output = subprocess.check_output(
         subprocess_cmd, stderr=subprocess.STDOUT)
     logging.info('Validating and converting %r to %r succeeded with output: %r',
@@ -177,6 +179,8 @@ def _validate_and_convert_profraw(profraw_file, output_profdata_files,
     else:
       profile_valid = True
   except subprocess.CalledProcessError as error:
+    logging.warning('Validating and converting %r to %r failed with output: %r',
+                    profraw_file, output_profdata_file, error.output)
     validation_output = error.output
 
   # 2. Add the profile to the appropriate list(s).