Fix issue with doclava download when building varying revisions

build/android/download_doclava.py

Index: build/android/download_doclava.py
diff --git a/build/android/download_doclava.py b/build/android/download_doclava.py
index f9f9ea2f4c4a4ab039347a8a75a7f9e45bb94bff..32400293e1c8f5d913b3956f070946225df2d3ae 100755
--- a/build/android/download_doclava.py
+++ b/build/android/download_doclava.py
@@ -25,14 +25,22 @@ def main():
     return 0
   if not os.path.exists(ANDROID_ONLY_DIR):
     return 0
+  outdir = os.path.join('src', 'buildtools', 'android', 'doclava')
+  tarball = outdir + '.tar.gz'
+  shafile = tarball + '.sha1'
+  # If the expanded directory does not exist, delete the tarball
+  # otherwise if the tarball exists and the SHA1 hash matches,
+  # download_from_google_storage will not download and
+  # extract, and any tools depending on the expanded directory will fail.
+  if os.path.exists(tarball) and not os.path.exists(outdir):
+    os.unlink(tarball)
   subprocess.check_call([
       'download_from_google_storage',
       '--no_resume',
       '--no_auth',
       '--bucket', 'chromium-doclava',
       '--extract',
-      '-s',
-      os.path.join('src', 'buildtools', 'android', 'doclava.tar.gz.sha1')])
+      '-s', shafile])
   return 0
 
 if __name__ == '__main__':