Replace the header from source code files using the following script:
```Python
for dir_path, dir_names, file_names in os.walk("flare-floss"):
for file_name in file_names:
try:
file_path = f"{dir_path}/{file_name}"
f = open(file_path, "rb+")
content = f.read()
m = re.search(OLD_HEADER, content)
if not m:
continue
print(f"{file_path}: {m.group('year')}")
content = content.replace(m.group(0), NEW_HEADER % m.group("year"))
f.seek(0)
f.write(content)
except:
continue
```
Some files had the copyright headers inside a `"""` comment and needed
manual changes before applying the script.
The old header had the confusing sentence `All rights reserved`, which
does not make sense for an open source license. Replace the header by
the default Google header that corrects this issue and keep floss
consistent with other Google projects.
