[SuperSize] Fix .sizediff generation inconsistency due to sorting.

This CL fixes the problem where .sizediff files created by
SuperSize-save_diff differ across identical runs. This happens because
the order of alised symbols from _ExpandSparseSymbols() become
arbitrarily ordered. The fix is to refine sort key in SortSymbols().

Change-Id: Ida24d0d97e261ce9aa65ed3a393e9e754c0951d3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2426552Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Commit-Queue: Samuel Huang <huangs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#810194}

tools/binary_size/libsupersize/file_format.py

@@ -124,7 +124,6 @@ _SIZE_HEADER_MULTI_CONTAINER = b'Size File Format v1.1\n'
 _SIZEDIFF_HEADER = b'DIFF\n'
 _SIZEDIFF_VERSION = 1
 
-
 class _Writer:
   """Helper to format and write data to a file object."""
 
@@ -163,8 +162,13 @@ def SortSymbols(raw_symbols):
   #     (and not using .sort()), or have it specify a total ordering (which must
   #     also include putting padding-only symbols before others of the same
   #     address). Note: The sort as-is takes ~1.5 seconds.
+  # s.size_without_padding > 0 prevents CalculatePadding() from incorrectly
+  #   detecting duplicate symbols.
+  # (s.full_name, s.object_path) are important for sort stability when called by
+  #   _ExpandSparseSymbols().
   raw_symbols.sort(
-      key=lambda s: (s.IsPak(), s.IsBss(), s.section_name, s.address))
+      key=lambda s: (s.IsPak(), s.IsBss(), s.section_name, s.address, s.
+                     size_without_padding > 0, s.full_name, s.object_path))
   logging.info('Processed %d symbols', len(raw_symbols))
 
 
@@ -229,7 +233,6 @@ def _ExpandSparseSymbols(sparse_symbols):
   logging.debug('Done expanding sparse_symbols')
   return models.SymbolGroup(raw_symbols)
 
-
 def _SaveSizeInfoToFile(size_info,
                         file_obj,
                         include_padding=False,

tools/binary_size/libsupersize/testdata/Archive_Pak_Files.golden

@@ -158,8 +158,8 @@ Section .other: has 100.0% of 90351129 bytes accounted for from 23 symbols. 0 by
 .pak.nontranslated@0(size_without_padding=0,padding=18,full_name=Overhead: ../../../mock_apk/assets/resources.pak,object_path=,source_path=,flags={},num_aliases=1,component=)
 .pak.nontranslated@2f03(size_without_padding=502,padding=0,full_name=../../chrome/browser/browser_resources.grd: IDR_PDF_COMPOSITOR_MANIFEST,object_path=,source_path=,flags={uncompressed},num_aliases=1,component=)
 .pak.nontranslated@2f04(size_without_padding=217,padding=0,full_name=../../chrome/browser/browser_resources.grd: IDR_CHROME_RENDERER_SERVICE_MANIFEST,object_path=,source_path=,flags={},num_aliases=1,component=)
-.pak.translations@0(size_without_padding=0,padding=18,full_name=Overhead: ../../../mock_apk/assets/en-US.pak,object_path=,source_path=,flags={},num_aliases=1,component=)
 .pak.translations@0(size_without_padding=0,padding=0,full_name=Overhead: Pak compression artifacts,object_path=,source_path=,flags={},num_aliases=1,component=)
+.pak.translations@0(size_without_padding=0,padding=18,full_name=Overhead: ../../../mock_apk/assets/en-US.pak,object_path=,source_path=,flags={},num_aliases=1,component=)
 .pak.translations@3ac6(size_without_padding=40,padding=0,full_name=../../components/app_modal_strings.grdp: IDS_BEFOREUNLOAD_MESSAGEBOX_MESSAGE,object_path=,source_path=,flags={},num_aliases=1,component=)
 .pak.translations@3d7c(size_without_padding=24,padding=0,full_name=../../components/policy_strings.grdp: IDS_POLICY_TYPE_ERROR,object_path=,source_path=,flags={},num_aliases=1,component=)
 .pak.translations@3d82(size_without_padding=25,padding=0,full_name=../../components/policy_strings.grdp: IDS_POLICY_LIST_ENTRY_ERROR,object_path=,source_path=,flags={},num_aliases=1,component=)