Needed when a roll happens, or when a size alert contains multiple commits.

I've been using a bash script for this, but it's too shameful to commit :P. Instead, I'll just paste it below.

The main learnings from having done this in the past:

1. Sanity check the number of commits is reasonable before starting
2. Abort if 3 builds in a row fail (this was more important when I was letting it run for weeks at a time)
3. Allow specifying sub-repo




#!/bin/bash

i=1
failed=0
BUILD_OUTPUT_DIR=out-gn/Release
SCRIPT_OUTPUT_DIR=out-gn/resource-sizes
CAUGHT_UP_HASH=04f54bf6
TARGET=chrome_public_apk
APK=ChromePublic.apk
LIB=lib.unstripped/libchrome.so
SUBREPO=v8
#04f54bf6..dc1b150e

if [[ -e $SCRIPT_OUTPUT_DIR ]]; then
  echo "Error: $SCRIPT_OUTPUT_DIR already exists."
  exit 1
fi

num_commits=$(cd $SUBREPO && git log $CAUGHT_UP_HASH^..HEAD --oneline | wc -l)
echo "$num_commits commits to build."

while true; do
  if [[ $SUBREPO = . ]]; then
    CHROME_HEADLESS=1 gclient sync
  fi
  rev=$(cd $SUBREPO && git rev-parse HEAD)
  echo "At rev: $rev"
  if [[ -z "$(cd $SUBREPO && git log $CAUGHT_UP_HASH^..HEAD -n1)" ]]; then
    echo "Caught up!"
    exit 0
  fi
  broken=
  if ! ( gn gen $BUILD_OUTPUT_DIR && cr-ninja.sh -C $BUILD_OUTPUT_DIR -j600 $TARGET ); then
    find $BUILD_OUTPUT_DIR -name "*.jar" -delete
    if ! ( cr-ninja.sh -C $BUILD_OUTPUT_DIR -j600 $TARGET ); then
      gn clean $BUILD_OUTPUT_DIR
      if ! ( gn gen $BUILD_OUTPUT_DIR && cr-ninja.sh -C $BUILD_OUTPUT_DIR -j600 $TARGET ); then
        broken=" broken"
      fi
    fi
  fi
  size="?"
  # mkdir after build so that it's not in the way if things fail early.
  mkdir -p $SCRIPT_OUTPUT_DIR
  if [[ -z "$broken" ]]; then
    out_base="$SCRIPT_OUTPUT_DIR/$i-$rev"
    cp $BUILD_OUTPUT_DIR/$LIB.map.gz $out_base.map.gz
    build/android/resource_sizes.py $BUILD_OUTPUT_DIR/apks/$APK --chartjson --no-output-dir > $out_base.txt
    mv results-chart.json $out_base.json
    size=$(python -c "import json; print json.load(open('$out_base.json'))['charts']['${APK}_Specifics']['normalized apk size']['value']")
    failed=0
  else
    failed=$(($failed + 1))
    if [[ $failed -gt 3 ]]; then
      echo 'Four failures in a row. Stopping.'
      exit 1
    fi
  fi
  filesize=$(stat --format %s $BUILD_OUTPUT_DIR/apks/$APK)
  echo "$i,$rev,$filesize,$size$broken" >> $SCRIPT_OUTPUT_DIR/all-normalized-sizes.txt
  i=$(($i + 1))
  (cd $SUBREPO && git checkout HEAD^)
done