Bug 826385 - Reduce pause/resume notifications to gecko; r=mfinkle

mobile/android/base/GeckoActivity.java.in

@@ -2,11 +2,23 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
  * You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+#filter substitution
+
 package org.mozilla.gecko;
 
 import android.app.Activity;
+import android.content.ComponentName;
+import android.content.Intent;
+
+interface GeckoActivityStatus {
+    public boolean isGeckoActivityOpened();
+    public boolean isFinishing();  // typically from android.app.Activity
+};
+
+public class GeckoActivity extends Activity implements GeckoActivityStatus {
+    // has this activity recently started another Gecko activity?
+    private boolean mGeckoActivityOpened = false;
 
-public class GeckoActivity extends Activity {
     @Override
     public void onPause() {
         super.onPause();
@@ -22,9 +34,39 @@ public class GeckoActivity extends Activity {
 
         if (getApplication() instanceof GeckoApplication) {
             ((GeckoApplication) getApplication()).onActivityResume(this);
+            mGeckoActivityOpened = false;
         }
     }
 
+    @Override
+    public void startActivity(Intent intent) {
+        checkIfGeckoActivity(intent);
+        super.startActivity(intent);
+    }
+
+    @Override
+    public void startActivityForResult(Intent intent, int request) {
+        checkIfGeckoActivity(intent);
+        super.startActivityForResult(intent, request);
+    }
+
+    private void checkIfGeckoActivity(Intent intent) {
+        // Whenever we call our own activity, the component and it's package name is set.
+        // If we call an activity from another package, or an open intent (leaving android to resolve)
+        // component has a different package name or it is null.
+        ComponentName component = intent.getComponent();
+        mGeckoActivityOpened = false;
+        if (component != null &&
+            component.getPackageName() != null &&
+            component.getPackageName().equals("@ANDROID_PACKAGE_NAME@")) {
+            mGeckoActivityOpened = true;
+        }
+    }
+
+    public boolean isGeckoActivityOpened() {
+        return mGeckoActivityOpened;
+    }
+
     public boolean isApplicationInBackground() {
         return ((GeckoApplication) getApplication()).isApplicationInBackground();
     }

mobile/android/base/GeckoApplication.java

@@ -10,6 +10,7 @@ public class GeckoApplication extends Application {
 
     private boolean mInited;
     private boolean mInBackground;
+    private boolean mPausedGecko;
 
     private LightweightTheme mLightweightTheme;
 
@@ -32,17 +33,28 @@ public class GeckoApplication extends Application {
         mInited = true;
     }
 
-    protected void onActivityPause(GeckoActivity activity) {
+    protected void onActivityPause(GeckoActivityStatus activity) {
         mInBackground = true;
 
-        GeckoAppShell.sendEventToGecko(GeckoEvent.createPauseEvent(true));
+        if ((activity.isFinishing() == false) &&
+            (activity.isGeckoActivityOpened() == false)) {
+            // Notify Gecko that we are pausing; the cache service will be
+            // shutdown, closing the disk cache cleanly. If the android
+            // low memory killer subsequently kills us, the disk cache will
+            // be left in a consistent state, avoiding costly cleanup and
+            // re-creation. 
+            GeckoAppShell.sendEventToGecko(GeckoEvent.createPauseEvent(true));
+            mPausedGecko = true;
+        }
         GeckoConnectivityReceiver.getInstance().stop();
         GeckoNetworkManager.getInstance().stop();
     }
 
-    protected void onActivityResume(GeckoActivity activity) {
-        if (GeckoThread.checkLaunchState(GeckoThread.LaunchState.GeckoRunning))
+    protected void onActivityResume(GeckoActivityStatus activity) {
+        if (mPausedGecko) {
             GeckoAppShell.sendEventToGecko(GeckoEvent.createResumeEvent(true));
+            mPausedGecko = false;
+        }
         GeckoConnectivityReceiver.getInstance().start();
         GeckoNetworkManager.getInstance().start();
 

mobile/android/base/GeckoPreferences.java

@@ -43,7 +43,7 @@ import java.util.ArrayList;
 
 public class GeckoPreferences
     extends PreferenceActivity
-    implements OnPreferenceChangeListener, GeckoEventListener
+    implements OnPreferenceChangeListener, GeckoEventListener, GeckoActivityStatus
 {
     private static final String LOGTAG = "GeckoPreferences";
 
@@ -85,6 +85,24 @@ public class GeckoPreferences
         unregisterEventListener("Sanitize:Finished");
     }
 
+    @Override
+    public void onPause() {
+        super.onPause();
+
+        if (getApplication() instanceof GeckoApplication) {
+            ((GeckoApplication) getApplication()).onActivityPause(this);
+        }
+    }
+
+    @Override
+    public void onResume() {
+        super.onResume();
+
+        if (getApplication() instanceof GeckoApplication) {
+            ((GeckoApplication) getApplication()).onActivityResume(this);
+        }
+    }
+
     public void handleMessage(String event, JSONObject message) {
         try {
             if (event.equals("Sanitize:Finished")) {
@@ -445,4 +463,8 @@ public class GeckoPreferences
     private void unregisterEventListener(String event) {
         GeckoAppShell.getEventDispatcher().unregisterEventListener(event, this);
     }
+
+    public boolean isGeckoActivityOpened() {
+        return false;
+    }
 }