To enable the crash reporter on local builds:
export MOZ_CRASHREPORTER=1 and re-run mach config to pick up the change

adb logcat -s "GeckoMemoryMonitor"
adb shell am broadcast -a org.mozilla.gecko.FORCE_MEMORY_PRESSURE

Busy sleep in JS:
log("sleeping 20 s");
this._sleep(20000);
log("returned from sleep");

_sleep: function sleepFor(sleepDuration) {
  var now = new Date().getTime();
  while(new Date().getTime() < now + sleepDuration){ /* do nothing */ }
}

Fuzzy hg import
hg import --config ui.patch="patch --merge" fuzzy.patch


GDB:
Ctrl + C = break
continue / c
step / s = single step
next / = step over
break <file:line or functionname> = set breakpoint
bt = backtrace calling stack
print <variable name>

./gradlew clean app:assembleLocalAustralisDebug
./mach gradle clean app:assembleLocalAustralisDebug
./mach build && ./mach package && ./mach gradle clean app:assembleLocalAustralisDebug
./mach gradle clean app:assembleOfficialAustralisDebug && ./mach gradle app:assembleOfficialAustralisDebugAndroidTest

Strg + Alt + Shift + I: bring up inspections in Android Studio (e.g. unused resources)

HG alias for empty commit
[alias] empty = !touch tmp ; $HG add tmp ; $HG commit tmp -m "<enter commit message>" ; $HG rm tmp ; $HG commit tmp --amend "$@"
on Windows:
empty = !touch tmp && hg add tmp && hg commit tmp -m "<enter commit message>" && hg rm tmp && hg commit tmp --amend "$@"

Redirect output for faster builds
./mach build > build.log 2>&1

Update rust:
rustup update

Screenshot via adb:
adb shell screencap -p | sed 's/\r$//' > screen.png
adb shell screencap -p | perl -pe 's/\x0D\x0A/\x0A/g' > screen.png
adb exec-out screencap -p > screen.png

android.os.Debug.waitForDebugger();

Enable Desktop remote debugging:
Shift + F2 for developer console, then "listen <port>"

devtools.debugger.new-debugger-frontend

GeckoConsole|GeckoSession|GeckoBrowser:

root shell:
sudo -s

Reclaim empty virtual disk space:
e4defrag /dev/sda1
dd if=/dev/zero of=wipefile bs=1024x1024; rm wipefile
Compact disk in VMWare