Fix navigation bar flaky tests

The flakiness is because the timing issue on hasNavigationBar.
When a new display is added, onDisplayAdded is called and we may try to
add nav bar before DisplayPolicy#configure is called, which sets
mHasNavigationBar value. Therefore, we may get false from
hasNavigationBar even if a display does support system decorations.

Fixes: 120748674
Test: atest ActivityManagerMultiDisplayTests
Test: atest
ActivityManagerMultiDisplayTests#testNavBarShowingOnDisplayWithDecor *
100

Change-Id: Idb3c3d0874c15a466d179cc471ade5cea890e20e
diff --git a/services/core/java/com/android/server/wm/DisplayPolicy.java b/services/core/java/com/android/server/wm/DisplayPolicy.java
index 8b8cadc..6d3c693 100644
--- a/services/core/java/com/android/server/wm/DisplayPolicy.java
+++ b/services/core/java/com/android/server/wm/DisplayPolicy.java
@@ -505,23 +505,6 @@
         // TODO: Make it can take screenshot on external display
         mScreenshotHelper = displayContent.isDefaultDisplay
                 ? new ScreenshotHelper(mContext) : null;
-    }
-
-    void systemReady() {
-        mSystemGestures.systemReady();
-    }
-
-    private int getDisplayId() {
-        return mDisplayContent.getDisplayId();
-    }
-
-    void onDisplayRemoved() {
-        mDisplayContent.unregisterPointerEventListener(mSystemGestures);
-    }
-
-    void configure(int width, int height, int shortSizeDp) {
-        // Allow the navigation bar to move on non-square small devices (phones).
-        mNavigationBarCanMove = width != height && shortSizeDp < 600;
 
         if (mDisplayContent.isDefaultDisplay) {
             mHasStatusBar = true;
@@ -541,6 +524,23 @@
         }
     }
 
+    void systemReady() {
+        mSystemGestures.systemReady();
+    }
+
+    private int getDisplayId() {
+        return mDisplayContent.getDisplayId();
+    }
+
+    void onDisplayRemoved() {
+        mDisplayContent.unregisterPointerEventListener(mSystemGestures);
+    }
+
+    void configure(int width, int height, int shortSizeDp) {
+        // Allow the navigation bar to move on non-square small devices (phones).
+        mNavigationBarCanMove = width != height && shortSizeDp < 600;
+    }
+
     void updateConfigurationDependentBehaviors() {
         mNavBarOpacityMode = mContext.getResources().getInteger(R.integer.config_navBarOpacityMode);
     }