Add a setting to hide memory pressure from a-c

This adds a setting in "Customize" to fix
https://github.com/fork-maintainers/iceraven-browser/issues/115

app/src/main/java/org/mozilla/fenix/FenixApplication.kt

@@ -326,7 +326,22 @@ open class FenixApplication : LocaleAwareApplication(), Provider {
 
         runOnlyInMainProcess {
             components.core.icons.onTrimMemory(level)
-            components.core.store.dispatch(SystemAction.LowMemoryAction(level))
+            
+            // We want to be judicious in passing low mamory messages to
+            // android-components, because it is (at time of writing) hardcoded
+            // to drop tab states (and any user data in them) as soon as we
+            // reach "moderate" memory pressure on the system, even if the
+            // browser is in no danger of being killed. See
+            // https://github.com/mozilla-mobile/android-components/blob/38186676d46c555b5a24268e5fa361e45e57102c/components/browser/session/src/main/java/mozilla/components/browser/session/engine/middleware/TrimMemoryMiddleware.kt#L53-L64
+            // for the relvant android-components code and
+            // https://stuff.mit.edu/afs/sipb/project/android/docs/reference/android/content/ComponentCallbacks2.html
+            // for the list of memory pressure levels.
+            val settings = this.settings()
+            if (settings.shouldRelinquishMemoryUnderPressure) {
+                // We will give up our RAM when asked nicely
+                components.core.store.dispatch(SystemAction.LowMemoryAction(level))
+            }
+            // Otherwise we will die for our RAM, if pressed.
         }
     }
 

app/src/main/java/org/mozilla/fenix/settings/CustomizationFragment.kt

@@ -64,6 +64,7 @@ class CustomizationFragment : PreferenceFragmentCompat() {
         setupHomeCategory()
         setupGesturesCategory()
         setupAddonsCustomizationCategory()
+        setupSystemBehaviorCategory()
     }
 
     private fun setupRadioGroups() {
@@ -256,4 +257,11 @@ class CustomizationFragment : PreferenceFragmentCompat() {
             onPreferenceChangeListener = SharedPreferenceUpdater()
         }
     }
+    
+    private fun setupSystemBehaviorCategory() {
+        requirePreference<SwitchPreference>(R.string.pref_key_relinquish_memory_under_pressure).apply {
+            isChecked = context.settings().shouldRelinquishMemoryUnderPressure
+            onPreferenceChangeListener = SharedPreferenceUpdater()
+        }
+    }
 }

app/src/main/java/org/mozilla/fenix/utils/Settings.kt

@@ -550,6 +550,11 @@ class Settings(private val appContext: Context) : PreferencesHolder {
         appContext.getPreferenceKey(R.string.pref_key_strip_url),
         default = true
     )
+    
+    var shouldRelinquishMemoryUnderPressure by booleanPreference(
+        appContext.getPreferenceKey(R.string.pref_key_relinquish_memory_under_pressure),
+        default = true
+    )
 
     /**
      * Check each active accessibility service to see if it can perform gestures, if any can,

app/src/main/res/values/preference_keys.xml

@@ -133,7 +133,7 @@
     <string name="pref_key_dynamic_toolbar" translatable="false">pref_key_dynamic_toolbar</string>
     <string name="pref_key_swipe_toolbar_switch_tabs" translatable="false">pref_key_swipe_toolbar_switch_tabs</string>
     <string name="pref_key_swipe_toolbar_show_tabs" translatable="false">pref_key_swipe_toolbar_show_tabs</string>
-
+    
     <!-- Tabs Tray Customization Settings -->
     <string name="pref_tabs_tray_settings_category" translatable="false">pref_tabs_tray_settings_category</string>
     <string name="pref_key_tabs_tray_compact_tab" translatable="false">pref_key_tabs_tray_compact_tab</string>
@@ -151,6 +151,10 @@
     <string name="pref_addons_settings_category" translatable="false">pref_addons_settings_category</string>
     <string name="pref_key_addons_custom_account" translatable="false">pref_key_addons_custom_account</string>
     <string name="pref_key_addons_custom_collection" translatable="false">pref_key_addons_custom_collection</string>
+    
+    <!-- System Customization Settings -->
+    <string name="pref_system_behavior_settings_category" translatable="false">pref_system_behavior_settings_category</string>
+    <string name="pref_key_relinquish_memory_under_pressure" translatable="false">pref_key_relinquish_memory_under_pressure</string>
 
     <!-- Tracking Protection Settings -->
     <string name="pref_key_etp_learn_more" translatable="false">pref_key_etp_learn_more</string>

app/src/main/res/values/strings.xml

@@ -1585,6 +1585,13 @@
     <string name="addons_custom_source_account">Set custom add-ons account</string>
     <!-- Label for add-ons custom source collection preference -->
     <string name="addons_custom_source_collection">Set custom add-ons collection</string>
+    
+    <!-- Preference category for system behavior customization -->
+    <string name="preferences_system_behavior">Configure system behavior</string>
+    <!-- Title for relinquish memory preference in customization settings -->
+    <string name="preferences_relinquish_memory_title">Suspend tabs to avoid being killed for memory</string>
+    <!-- Description for relinquish memory preference in customization settings -->
+    <string name="preferences_relinquish_memory_description">If enabled, tabs will be suspended and page state lost when the system is low on memory</string>
 
     <!-- Label for enable compact tabs in tabs tray preference -->
     <string name="enable_compact_tabs">Enable compact tabs</string>

app/src/main/res/xml/customization_preferences.xml

@@ -138,4 +138,17 @@
             android:title="@string/addons_custom_source_collection" />
     </androidx.preference.PreferenceCategory>
     
+    <androidx.preference.PreferenceCategory
+        android:key="@string/pref_system_behavior_settings_category"
+        android:layout="@layout/preference_cat_style"
+        android:title="@string/preferences_system_behavior"
+        app:allowDividerAbove="true"
+        app:iconSpaceReserved="false">
+            <SwitchPreference
+            android:defaultValue="true"
+            android:key="@string/pref_key_relinquish_memory_under_pressure"
+            android:summary="@string/preferences_relinquish_memory_description"
+            android:title="@string/preferences_relinquish_memory_title" />
+    </androidx.preference.PreferenceCategory>
+    
 </androidx.preference.PreferenceScreen>