Improve AyncTask throughput inside WidgetPreviewLoader

b/21133230
> Synchronized block was creating a bottleneck for the AsyncTasks.
> Remove calls that doesn't need to be synchronized outside synchronized block.
> Also removed setAlpha call as after the bottleneck was removed,
Inefficient alpha view usage alert started popping up in traceview.
Due to less jankness, removing the fadein animation doesn't have any
visible effect.

Link to lock congestion visualization:
https://x20web.corp.google.com/~hyunyoungs/no_crawl/traceview/traceview_lockcontention.html

Result: gfx-avg-jank delta = "-1"
Change-Id: If12817df0730f346cdba7e2f38f232eb9a4336c0

2 files changed, 11 insertions, 1 deletions

diff --git a/src/com/android/launcher3/widget/WidgetCell.java b/src/com/android/launcher3/widget/WidgetCell.java
index 2714f5182..7496ea2ef 100644
--- a/src/com/android/launcher3/widget/WidgetCell.java
+++ b/src/com/android/launcher3/widget/WidgetCell.java
@@ -26,6 +26,7 @@ import android.util.Log;
 import android.view.MotionEvent;
 import android.view.View;
 import android.view.View.OnLayoutChangeListener;
+import android.view.ViewPropertyAnimator;
 import android.widget.LinearLayout;
 import android.widget.TextView;
 
@@ -175,7 +176,8 @@ public class WidgetCell extends LinearLayout implements OnLayoutChangeListener {
         if (bitmap != null) {
             mWidgetImage.setBitmap(bitmap);
             mWidgetImage.setAlpha(0f);
-            mWidgetImage.animate().alpha(1.0f).setDuration(FADE_IN_DURATION_MS);
+            ViewPropertyAnimator anim = mWidgetImage.animate();
+            anim.alpha(1.0f).setDuration(FADE_IN_DURATION_MS);
         }
     }
 
diff --git a/src/com/android/launcher3/widget/WidgetImageView.java b/src/com/android/launcher3/widget/WidgetImageView.java
index 6f8fd897b..b0fbe1ed9 100644
--- a/src/com/android/launcher3/widget/WidgetImageView.java
+++ b/src/com/android/launcher3/widget/WidgetImageView.java
@@ -64,6 +64,14 @@ public class WidgetImageView extends View {
         }
     }
 
+    /**
+     * Prevents the inefficient alpha view rendering.
+     */
+    @Override
+    public boolean hasOverlappingRendering() {
+        return false;
+    }
+
     private void updateDstRectF() {
         if (mBitmap.getWidth() > getWidth()) {
             float scale = ((float) getWidth()) / mBitmap.getWidth();