public enum BuildCause {
  // reasons for full build
  NO_DEVICE(BuildMode.FULL),
  APP_NOT_INSTALLED(BuildMode.FULL),
  MISMATCHING_TIMESTAMPS(BuildMode.FULL),
  API_TOO_LOW_FOR_INSTANT_RUN(BuildMode.FULL),
  FIRST_INSTALLATION_TO_DEVICE(BuildMode.FULL), // first installation in this Android Studio session
  FREEZE_SWAP_REQUIRES_API21(BuildMode.FULL),

  // reasons for forced cold swap build
  USER_REQUESTED_COLDSWAP(BuildMode.COLD), // User pressed Run, and only Run button was enabled (name not ideal, but matches existing proto)
  USER_CHOSE_TO_COLDSWAP(BuildMode.COLD),  // Both Run and Hotswap were enabled, and user chose Run
  APP_NOT_RUNNING(BuildMode.COLD),
  APP_USES_MULTIPLE_PROCESSES(BuildMode.COLD),
  ANDROID_TV_UNSUPPORTED(BuildMode.COLD),
  MANIFEST_RESOURCE_CHANGED(BuildMode.COLD),

  INCREMENTAL_BUILD(BuildMode.HOT),
}

@NotNull
private BuildCause computeBuildCause(@Nullable IDevice device) {
  ...
  if (manifestResourceChanged(device)) {
    return BuildCause.MANIFEST_RESOURCE_CHANGED;
  }
  ...	
  if (myRunContext.isForceColdswap()) {
    return myRunContext.couldHaveInvokedHotswap() ? BuildCause.USER_CHOSE_TO_COLDSWAP : BuildCause.USER_REQUESTED_COLDSWAP;
  }
  ...
  if (myInstantRunContext.usesMultipleProcesses()) {
    return BuildCause.APP_USES_MULTIPLE_PROCESSES;
  }
  ...
}

private static List<String> getInstantRunArguments(@NotNull BuildMode buildMode) {
  StringBuilder sb = new StringBuilder(50);
  sb.append("-P");
  sb.append(PROPERTY_OPTIONAL_COMPILATION_STEPS);
  sb.append("=");
  sb.append(OptionalCompilationStep.INSTANT_DEV.name());

  switch (buildMode) {
    case HOT:
      break;
    case COLD:
      sb.append(",").append(OptionalCompilationStep.RESTART_ONLY.name());
      break;
    case FULL:
      sb.append(",").append(OptionalCompilationStep.FULL_APK.name());
      break;
  }

  String compilationSteps = sb.toString();

  // Starting with Studio 2.3, we always do a split APK install on cold swaps
  String coldSwapMode = AndroidGradleSettings.createProjectProperty(AndroidProject.PROPERTY_SIGNING_COLDSWAP_MODE, "MULTIAPK");

  return ImmutableList.of(compilationSteps, coldSwapMode);
}

// InstantRunTaskManager.java
/** Creates all InstantRun related transforms after compilation. */
@NonNull
public PreColdSwapTask createPreColdswapTask(@NonNull ProjectOptions projectOptions) {

    TransformVariantScope transformVariantScope = variantScope.getTransformVariantScope();
    InstantRunBuildContext context = variantScope.getInstantRunBuildContext();

    if (transformVariantScope.getGlobalScope().isActive(OptionalCompilationStep.FULL_APK)) {
        context.setVerifierStatus(InstantRunVerifierStatus.FULL_BUILD_REQUESTED);
    } else if (transformVariantScope.getGlobalScope().isActive(
            OptionalCompilationStep.RESTART_ONLY)) {
        context.setVerifierStatus(InstantRunVerifierStatus.COLD_SWAP_REQUESTED);
    }

    PreColdSwapTask preColdSwapTask =
            taskFactory.create(
                    new PreColdSwapTask.ConfigAction(
                            "preColdswap", transformVariantScope, variantScope));

    if (verifierTask != null) {
        preColdSwapTask.dependsOn(verifierTask);
    }

    return preColdSwapTask;
}

// InstantRunBuildContext.java
/**
 * Sets the verifier status for the current build.
 *
 * @param verifierStatus
 */
public void setVerifierStatus(@NonNull InstantRunVerifierStatus verifierStatus) {

    LOG.info(
            "Receiving verifier result: {}. Current Verifier/Build mode is {}/{}.",
            verifierStatus,
            currentBuild.getVerifierStatus(),
            currentBuild.buildMode);

    // get the new build mode for this verifier status as it may change the one we
    // currently use.
    InstantRunBuildMode newBuildMode =
            currentBuild.buildMode.combine(
                    verifierStatus.getInstantRunBuildModeForPatchingPolicy(patchingPolicy));

    // save the verifier status, even if it does not end up being used as the main status,
    // this can be useful to check later on that certain condition were not met.
    currentBuild.allStatuses.add(verifierStatus);

    // if our current status is not set, or the new build mode is higher, reset everything.
    if (currentBuild.getVerifierStatus() == InstantRunVerifierStatus.NO_CHANGES
            || currentBuild.getVerifierStatus() == InstantRunVerifierStatus.COMPATIBLE
            || newBuildMode != currentBuild.buildMode) {
        currentBuild.verifierStatus = verifierStatus;
        currentBuild.buildMode = newBuildMode;
    }
    Preconditions.checkNotNull(
            patchingPolicy, "setApiLevel should be called before setVerifierStatus");

    LOG.info(
            "Verifier result is now : {}. Build mode is now {}.",
            currentBuild.getVerifierStatus(),
            currentBuild.buildMode);
}