Merge changes from topic 'AddPrinters'

* changes:
  Create PrintDiscoverySession for future print services
  Update printer availability when printSpooler is paused. This makes the window update syncronously when in multi-window mode.

packages/PrintSpooler/src/com/android/printspooler/ui/PrintActivity.java

@@ -336,8 +336,8 @@ public class PrintActivity extends Activity implements RemotePrintDocument.Updat
     }
 
     @Override
-    public void onResume() {
-        super.onResume();
+    public void onStart() {
+        super.onStart();
         if (mState != STATE_INITIALIZING && mCurrentPrinter != null) {
             mPrinterRegistry.setTrackedPrinter(mCurrentPrinter.getId());
         }
@@ -379,10 +379,15 @@ public class PrintActivity extends Activity implements RemotePrintDocument.Updat
             }
         }
 
+        super.onPause();
+    }
+
+    @Override
+    protected void onStop() {
         mPrinterAvailabilityDetector.cancel();
         mPrinterRegistry.setTrackedPrinter(null);
 
-        super.onPause();
+        super.onStop();
     }
 
     @Override

services/print/java/com/android/server/print/UserState.java

@@ -343,9 +343,7 @@ final class UserState implements PrintSpoolerCallbacks, PrintServiceCallbacks {
     public void createPrinterDiscoverySession(IPrinterDiscoveryObserver observer) {
         synchronized (mLock) {
             throwIfDestroyedLocked();
-            if (mActiveServices.isEmpty()) {
-                return;
-            }
+
             if (mPrinterDiscoverySession == null) {
                 // If we do not have a session, tell all service to create one.
                 mPrinterDiscoverySession = new PrinterDiscoverySessionMediator(mContext) {