milestone_apk_sizes.py: Skip DFM_base

We don't record this in the spreadsheet.

Bug: None
Change-Id: I606338deb26037842f77b9a171f6a5183a7b1d1f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2595843
Auto-Submit: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Sam Maier <smaier@chromium.org>
Commit-Queue: Sam Maier <smaier@chromium.org>
Cr-Commit-Position: refs/heads/master@{#838648}

tools/binary_size/milestone_apk_sizes.py

@@ -96,7 +96,7 @@ class _Artifact(object):
 
   def AddDfmSizes(self, metrics):
     for k, v in sorted(self._resource_sizes_json['charts'].items()):
-      if k.startswith('DFM_'):
+      if k.startswith('DFM_') and k != 'DFM_base':
         metrics['DFM: ' + k[4:]] = v['Size with hindi']['value']
 
   def PrintLibraryCompression(self):