Reapply "Add amm experiment."

See go/pixel-perf-amm-experiment for more info.

(This change is a reland of ag/30770395 after fixing issues that caused a revert.)

Bug: 365855872
Test: build/flash; set .Perf__amm_experiment=true, observe auto_migration_margins_enable value changing 1->0; set .Perf__amm_experiment="", observe the value changing 0->1
Flag: NONE controlled by Mendel instead
Change-Id: I833ea7cd104b95abf80f2286e91f96a102d8086a
Signed-off-by: Dmitry Skiba <dskiba@google.com>

performance/experiments/amm/Android.bp

@@ -0,0 +1,10 @@
+package {
+    default_applicable_licenses: ["Android-Apache-2.0"],
+}
+
+prebuilt_etc {
+    name: "pixel-amm-experiment.rc",
+    src: "pixel-amm-experiment.rc",
+    vendor: true,
+    sub_dir: "init",
+}

performance/experiments/amm/amm.mk

@@ -0,0 +1 @@
+PRODUCT_PACKAGES += pixel-amm-experiment.rc

performance/experiments/amm/pixel-amm-experiment.rc

@@ -0,0 +1,23 @@
+# Activate DISABLE_AMM hint.
+service pixel-amm-experiment-activate /vendor/bin/sendhint -m DISABLE_AMM
+    user root
+    disabled
+    oneshot
+
+# Deactivate DISABLE_AMM hint.
+service pixel-amm-experiment-deactivate /vendor/bin/sendhint -m DISABLE_AMM -e 0
+    user root
+    disabled
+    oneshot
+
+# AMM experiment (go/pixel-perf-amm-experiment).
+on property:vendor.perf.allow_experiments=1 && \
+    property:vendor.pixel.system.phenotype.Perf__amm_experiment=true
+    setprop vendor.powerhal.amm_enabled false
+    start pixel-amm-experiment-activate
+
+# Rampdown of the experiment.
+on property:vendor.perf.allow_experiments=1 && \
+    property:vendor.pixel.system.phenotype.Perf__amm_experiment=""
+    setprop vendor.powerhal.amm_enabled ""
+    start pixel-amm-experiment-deactivate

performance/experiments/experiments.mk

@@ -4,3 +4,4 @@ PRODUCT_PACKAGES += pixel-experiments-recovery.sh
 
 include device/google/gs-common/performance/experiments/kswapd/kswapd.mk
 include device/google/gs-common/performance/experiments/apf/apf.mk
+include device/google/gs-common/performance/experiments/amm/amm.mk