Run ShortcutHelper::AddToLauncherInBackgroundWithSkBitmap() on Worker thread instead of IO thread

testing/android/junit/java/src/org/chromium/testing/local/BackgroundShadowAsyncTask.java

Index: testing/android/junit/java/src/org/chromium/testing/local/BackgroundShadowAsyncTask.java
diff --git a/testing/android/junit/java/src/org/chromium/testing/local/BackgroundShadowAsyncTask.java b/testing/android/junit/java/src/org/chromium/testing/local/BackgroundShadowAsyncTask.java
index e542128b8d2d6b6040000826d920b1d687ac0ee7..ae53ee13e493fae415ed875c25e04da192e19b67 100644
--- a/testing/android/junit/java/src/org/chromium/testing/local/BackgroundShadowAsyncTask.java
+++ b/testing/android/junit/java/src/org/chromium/testing/local/BackgroundShadowAsyncTask.java
@@ -47,6 +47,16 @@ public class BackgroundShadowAsyncTask<Params, Progress, Result> extends
         }
     }
 
+    @Implementation
+    public final Result get() {
+        try {
+            runBackgroundTasks();
+            return BackgroundShadowAsyncTask.super.get();
+        } catch (Exception e) {
+            return null;
+        }
+    }
+
     public static void runBackgroundTasks() throws Exception {
         sExecutorService.submit(new Runnable() {
             @Override
@@ -55,4 +65,4 @@ public class BackgroundShadowAsyncTask<Params, Progress, Result> extends
             }
         }).get();
     }
-}
+}