If you look at gen/clank/java/monochrome_apk__process_resources.srcjar, you can see R.java files contain methods like:

public static void onResourcesLoaded(int packageId) {
    attr.allowShortcuts = (attr.allowShortcuts & 0x00ffffff) | (packageId << 24);
    attr.ambientEnabled = (attr.ambientEnabled & 0x00ffffff) | (packageId << 24);
    ...
}

These are called by reflection from the framework when packagedId != 7f (the default):
https://github.com/android/platform_frameworks_base/blob/4b1a8f46d6ec55796bf77fd8921a5a242a219278/core/java/android/app/LoadedApk.java#L824

Rather than using aapt, we generate these from our own templates here:
https://cs.chromium.org/chromium/src/build/android/gyp/process_resources.py?q=process_resour+ce&sq=package:chromium&l=214


I'd like to try a couple ideas to reduce code size:

Idea #1: Use a variable "shiftedPackageId"

public static void onResourcesLoaded(int packageId) {
    int shiftedPackageId = packageId << 24;
    attr.allowShortcuts = (attr.allowShortcuts & 0x00ffffff) | shiftedPackagedId;
    attr.ambientEnabled = (attr.ambientEnabled & 0x00ffffff) | shiftedPackagedId;
    ...
}


Idea #2: Use xor rather than masks

public static void onResourcesLoaded(int packageId) {
    assert(attr.allowShortcuts >> 24 == 0x7f)
    int packageIdTransform = (packageId ^ 0x7f) << 24;
    attr.allowShortcuts = attr.allowShortcuts ^ packageIdTransform;
    attr.ambientEnabled = attr.ambientEnabled ^ packageIdTransform;
    ...
}


To measure how much smaller this makes the code, we should build monochrome_public_apk with is_java_debug=false, and then list the uncompressed size of classes.dex via "unzip -lv apks/MonochromePublic.apk | grep classes"