Show shadow when entity header starts scrolling.

- Add a controller to manage add/remove onScrollChangedListener to
  recyclerviews.
- When recyclerview on each screen is scrolled to top, set actionbar
  elevation to 0, otherwise set it to non-zero.
- When screen is moved to background, detach the listener.
- Use the controller in entity header.

Change-Id: Iecf194d885098c98c392810f62893ae9189f3936
Fix: 37670670
Test: make RunSettingsRoboTests

src/com/android/settings/applications/ProcessStatsDetail.java

@@ -128,16 +128,17 @@ public class ProcessStatsDetail extends SettingsPreferenceFragment {
         final Activity activity = getActivity();
         final Preference pref = EntityHeaderController
                 .newInstance(activity, this, null /* appHeader */)
-            .setIcon(mApp.mUiTargetApp != null
-                ? IconDrawableFactory.newInstance(activity).getBadgedIcon(mApp.mUiTargetApp)
-                : new ColorDrawable(0))
-            .setLabel(mApp.mUiLabel)
-            .setPackageName(mApp.mPackage)
-            .setUid(mApp.mUiTargetApp != null
-                ? mApp.mUiTargetApp.uid
-                : UserHandle.USER_NULL)
-            .setButtonActions(ActionType.ACTION_APP_INFO, ActionType.ACTION_NONE)
-            .done(activity, getPrefContext());
+                .setRecyclerView(getListView(), getLifecycle())
+                .setIcon(mApp.mUiTargetApp != null
+                        ? IconDrawableFactory.newInstance(activity).getBadgedIcon(mApp.mUiTargetApp)
+                        : new ColorDrawable(0))
+                .setLabel(mApp.mUiLabel)
+                .setPackageName(mApp.mPackage)
+                .setUid(mApp.mUiTargetApp != null
+                        ? mApp.mUiTargetApp.uid
+                        : UserHandle.USER_NULL)
+                .setButtonActions(ActionType.ACTION_APP_INFO, ActionType.ACTION_NONE)
+                .done(activity, getPrefContext());
         getPreferenceScreen().addPreference(pref);
     }