Refactor onOptionsItemSelected behavior.

1. onOptionsItemSelected behavior now conforms to the contract set out in the docs.
2. onOptionsItemSelected for sub-Controllers now delegate to the super class when they have no behavior defined for an item.

Author: grepx

todoapp/app/src/main/java/com/example/android/architecture/blueprints/todoapp/BaseController.java

@@ -45,11 +45,11 @@ protected void onAttach(@NonNull View view) {
     public boolean onOptionsItemSelected(MenuItem item) {
         switch (item.getItemId()) {
             case android.R.id.home:
-                // Set the default behavior to be back navigation
-                getRouter().popCurrentController();
-                break;
+                // Set the default behavior to be back navigation.
+                getRouter().handleBack();
+                return true;
         }
-        return true;
+        return false;
     }
 
     @Override

todoapp/app/src/main/java/com/example/android/architecture/blueprints/todoapp/statistics/StatisticsController.java

@@ -78,9 +78,9 @@ public boolean onOptionsItemSelected(MenuItem item) {
             case android.R.id.home:
                 // Open the navigation drawer when the home icon is selected from the toolbar.
                 getDrawerLayout().openDrawer(GravityCompat.START);
-                break;
+                return true;
         }
-        return true;
+        return super.onOptionsItemSelected(item);
     }
 
     @Override

todoapp/app/src/main/java/com/example/android/architecture/blueprints/todoapp/taskdetail/TaskDetailController.java

@@ -122,7 +122,7 @@ public boolean onOptionsItemSelected(MenuItem item) {
                 mPresenter.deleteTask();
                 return true;
         }
-        return false;
+        return super.onOptionsItemSelected(item);
     }
 
     @Override

todoapp/app/src/main/java/com/example/android/architecture/blueprints/todoapp/tasks/TasksController.java

@@ -196,18 +196,18 @@ public boolean onOptionsItemSelected(MenuItem item) {
             case android.R.id.home:
                 // Open the navigation drawer when the home icon is selected from the toolbar.
                 getDrawerLayout().openDrawer(GravityCompat.START);
-                break;
+                return true;
             case R.id.menu_clear:
                 mPresenter.clearCompletedTasks();
-                break;
+                return true;
             case R.id.menu_filter:
                 showFilteringPopUpMenu();
-                break;
+                return true;
             case R.id.menu_refresh:
                 mPresenter.loadTasks(true);
-                break;
+                return true;
         }
-        return true;
+        return super.onOptionsItemSelected(item);
     }
 
     @Override