Add FeatureFlag for ENABLE_FOUR_COLUMNS.

Will be paired with new device profile used to dogfood
upcoming grid changes.

Bug: 175329686
Change-Id: Iab08d9ed0dec14fd6a05c4485ac4e066533d2540

src/com/android/launcher3/InvariantDeviceProfile.java

@@ -19,6 +19,7 @@ package com.android.launcher3;
 import static com.android.launcher3.Utilities.getDevicePrefs;
 import static com.android.launcher3.Utilities.getPointString;
 import static com.android.launcher3.config.FeatureFlags.APPLY_CONFIG_AT_RUNTIME;
+import static com.android.launcher3.config.FeatureFlags.ENABLE_FOUR_COLUMNS;
 import static com.android.launcher3.util.Executors.MAIN_EXECUTOR;
 import static com.android.launcher3.util.PackageManagerHelper.getPackageFilter;
 
@@ -215,6 +216,9 @@ public class InvariantDeviceProfile {
     }
 
     public static String getCurrentGridName(Context context) {
+        if (ENABLE_FOUR_COLUMNS.get()) {
+            return ENABLE_FOUR_COLUMNS.key;
+        }
         return Utilities.isGridOptionsEnabled(context)
                 ? Utilities.getPrefs(context).getString(KEY_IDP_GRID_NAME, null) : null;
     }

src/com/android/launcher3/config/FeatureFlags.java

@@ -190,6 +190,10 @@ public final class FeatureFlags {
             "EXPANDED_SMARTSPACE", false, "Expands smartspace height to two rows. "
               + "Any apps occupying the first row will be removed from workspace.");
 
+    public static final BooleanFlag ENABLE_FOUR_COLUMNS = new DeviceFlag(
+            "ENABLE_FOUR_COLUMNS", false, "Uses 4 columns in launcher grid."
+            + "Warning: This will permanently alter your home screen items and is not reversible.");
+
     public static void initialize(Context context) {
         synchronized (sDebugFlags) {
             for (DebugFlag flag : sDebugFlags) {