chore: Separate extensions by app (#3905)

extensions/youtube/stub/src/main/java/com/google/android/android/support/constraint/ConstraintLayout.java

@@ -0,0 +1,20 @@
+package com.google.android.android.support.constraint;
+
+import android.content.Context;
+import android.view.ViewGroup;
+
+/**
+ * "CompileOnly" class
+ * because android.support.android.support.constraint.ConstraintLayout is deprecated
+ * in favour of androidx.constraintlayout.widget.ConstraintLayout.
+ * <p>
+ * This class will not be included and "replaced" by the real package's class.
+ */
+public class ConstraintLayout extends ViewGroup {
+    public ConstraintLayout(Context context) {
+        super(context);
+    }
+
+    @Override
+    protected void onLayout(boolean changed, int l, int t, int r, int b) { }
+}

extensions/youtube/stub/src/main/java/com/google/android/apps/youtube/app/ui/SlimMetadataScrollableButtonContainerLayout.java

@@ -0,0 +1,25 @@
+package com.google.android.apps.youtube.app.ui;
+
+import android.content.Context;
+import android.util.AttributeSet;
+import android.view.ViewGroup;
+
+public class SlimMetadataScrollableButtonContainerLayout extends ViewGroup {
+
+    public SlimMetadataScrollableButtonContainerLayout(Context context) {
+        super(context);
+    }
+
+    public SlimMetadataScrollableButtonContainerLayout(Context context, AttributeSet attrs) {
+        super(context, attrs);
+    }
+
+    public SlimMetadataScrollableButtonContainerLayout(Context context, AttributeSet attrs, int defStyleAttr) {
+        super(context, attrs, defStyleAttr);
+    }
+
+    @Override
+    protected void onLayout(boolean b, int i, int i1, int i2, int i3) {
+
+    }
+}

extensions/youtube/stub/src/main/java/com/google/android/libraries/youtube/rendering/ui/pivotbar/PivotBar.java

@@ -0,0 +1,10 @@
+package com.google.android.libraries.youtube.rendering.ui.pivotbar;
+
+import android.content.Context;
+import android.widget.HorizontalScrollView;
+
+public class PivotBar extends HorizontalScrollView {
+    public PivotBar(Context context) {
+        super(context);
+    }
+}

extensions/youtube/stub/src/main/java/com/google/protos/youtube/api/innertube/InnertubeContext$ClientInfo.java

@@ -0,0 +1,5 @@
+package com.google.protos.youtube.api.innertube;
+
+public class InnertubeContext$ClientInfo {
+    public int r;
+}