Move offscreenTranslation calculation to LauncherRecentsView

Couple of benefits here:
- Doesn't rely on having a measured TaskView, since it already knows how
  to calculate the task size
- Code can be shared (planning to use this for quick switch from home)

Bug:
Change-Id: I517a78506ac95fcc37d9225a074427941d691903

quickstep/recents_ui_overrides/src/com/android/quickstep/LauncherActivityControllerHelper.java

@@ -273,17 +273,7 @@ public final class LauncherActivityControllerHelper implements ActivityControlHe
                     // from the side. Calculate the start translation based on current scale/scroll.
                     float currScale = recentsView.getScaleX();
                     float scrollOffsetX = recentsView.getScrollOffset();
-
-                    float offscreenX = NORMAL.getOverviewScaleAndTranslation(activity).translationX;
-                    // The first task is hidden, so offset by its width.
-                    int firstTaskWidth = recentsView.getTaskViewAt(0).getWidth();
-                    offscreenX -= (firstTaskWidth + recentsView.getPageSpacing()) * currScale;
-                    // Offset since scale pushes tasks outwards.
-                    offscreenX += firstTaskWidth * (currScale - 1) / 2;
-                    offscreenX = Math.max(0, offscreenX);
-                    if (recentsView.isRtl()) {
-                        offscreenX = -offscreenX;
-                    }
+                    float offscreenX = recentsView.getOffscreenTranslationX(currScale);
 
                     float fromTranslationX = attached ? offscreenX - scrollOffsetX : 0;
                     float toTranslationX = attached ? 0 : offscreenX - scrollOffsetX;

quickstep/recents_ui_overrides/src/com/android/quickstep/views/LauncherRecentsView.java

@@ -57,6 +57,8 @@ import com.android.quickstep.util.LayoutUtils;
 @TargetApi(Build.VERSION_CODES.O)
 public class LauncherRecentsView extends RecentsView<Launcher> implements StateListener {
 
+    private static final Rect sTempRect = new Rect();
+
     private final TransformParams mTransformParams = new TransformParams();
 
     public LauncherRecentsView(Context context) {
@@ -144,6 +146,25 @@ public class LauncherRecentsView extends RecentsView<Launcher> implements StateL
         LayoutUtils.calculateLauncherTaskSize(getContext(), dp, outRect);
     }
 
+    /**
+     * @return The translationX to apply to this view so that the first task is just offscreen.
+     */
+    public float getOffscreenTranslationX(float recentsScale) {
+        float offscreenX = NORMAL.getOverviewScaleAndTranslation(mActivity).translationX;
+        // Offset since scale pushes tasks outwards.
+        getTaskSize(sTempRect);
+        int taskWidth = sTempRect.width();
+        offscreenX += taskWidth * (recentsScale - 1) / 2;
+        if (mRunningTaskTileHidden) {
+            // The first task is hidden, so offset by its width.
+            offscreenX -= (taskWidth + getPageSpacing()) * recentsScale;
+        }
+        if (isRtl()) {
+            offscreenX = -offscreenX;
+        }
+        return offscreenX;
+    }
+
     @Override
     protected void onTaskLaunchAnimationUpdate(float progress, TaskView tv) {
         if (ENABLE_QUICKSTEP_LIVE_TILE.get()) {

quickstep/recents_ui_overrides/src/com/android/quickstep/views/RecentsView.java

@@ -272,7 +272,7 @@ public abstract class RecentsView<T extends BaseActivity> extends PagedView impl
 
     // Only valid until the launcher state changes to NORMAL
     protected int mRunningTaskId = -1;
-    private boolean mRunningTaskTileHidden;
+    protected boolean mRunningTaskTileHidden;
     private Task mTmpRunningTask;
 
     private boolean mRunningTaskIconScaledDown = false;