Update the sharing UI according to latest UX specs.

bug:3362473

Change-Id: Ic302c289e28061f53446f98e5b97573d57d9cfb8
diff --git a/core/java/android/widget/ActivityChooserModel.java b/core/java/android/widget/ActivityChooserModel.java
index 9fea506..bc44521 100644
--- a/core/java/android/widget/ActivityChooserModel.java
+++ b/core/java/android/widget/ActivityChooserModel.java
@@ -663,6 +663,17 @@
         }
     }
 
+    /**
+     * Gets the history size.
+     *
+     * @return The history size.
+     */
+    public int getHistorySize() {
+        synchronized (mInstanceLock) {
+            return mHistoricalRecords.size();
+        }
+    }
+
     @Override
     protected void finalize() throws Throwable {
         super.finalize();