taintdroid code reading 3.

I read a diff of services/java/com/android/server/LocationManagerService.java.
It is almost the same as the diff of telephony. When location update message is received, the location is stored in Taint object as following:

location.setLatitude(Taint.addTaintDouble(location.getLatitude(), tag));

But I cannot understand the reason why obtained value is set again, that is, why setLatitude is called.
And the other point I cannot understand is that how to distinguish the values. For example, the below is a code to store latitude and location.

    location.setLatitude(Taint.addTaintDouble(location.getLatitude(), tag));
    location.setLongitude(Taint.addTaintDouble(location.getLongitude(), tag));

where tag is given here as following:

    int tag = Taint.TAINT_LOCATION;
    if (LocationManager.GPS_PROVIDER.equals(provider)) {
        tag |= Taint.TAINT_LOCATION_GPS;
    }
    if (LocationManager.NETWORK_PROVIDER.equals(provider)) {
        tag |= Taint.TAINT_LOCATION_NET;
    }

Latitude and Longitude are added by addTaingDouble, but I cannot see how to distinguish latitude and longitude.
I paste the whole diff below.

diff --git a/services/java/com/android/server/LocationManagerService.java b/services/java/com/android/server/LocationManagerService.java
index bbb43d7..4a5846a 100644
--- a/services/java/com/android/server/LocationManagerService.java
+++ b/services/java/com/android/server/LocationManagerService.java
@@ -68,6 +68,10 @@ import com.android.internal.location.LocationProviderProxy;
 import com.android.internal.location.MockProvider;
 import com.android.internal.location.GpsNetInitiatedHandler;
 
+// begin WITH_TAINT_TRACKING
+import dalvik.system.Taint;
+// end WITH_TAINT_TRACKING
+
 /**
  * The service class that manages LocationProviders and issues location
  * updates and alerts.
@@ -1526,6 +1530,30 @@ public class LocationManagerService extends ILocationManager.Stub implements Run
                         Location location = (Location) msg.obj;
                         String provider = location.getProvider();
 
+   // begin WITH_TAINT_TRACKING
+   int tag = Taint.TAINT_LOCATION;
+   if (LocationManager.GPS_PROVIDER.equals(provider)) {
+       tag |= Taint.TAINT_LOCATION_GPS;
+   }
+   if (LocationManager.NETWORK_PROVIDER.equals(provider)) {
+       tag |= Taint.TAINT_LOCATION_NET;
+   }
+   location.setLatitude(Taint.addTaintDouble(location.getLatitude(), tag));
+   location.setLongitude(Taint.addTaintDouble(location.getLongitude(), tag));
+   if (location.hasAltitude()) {
+       location.setAltitude(Taint.addTaintDouble(location.getAltitude(), tag));
+   }    
+   if (location.hasSpeed()) {
+       location.setSpeed(Taint.addTaintFloat(location.getSpeed(), tag));
+   }    
+   if (location.hasBearing()) {
+       location.setBearing(Taint.addTaintFloat(location.getBearing(), tag));
+   }    
+   if (location.hasAccuracy()) {
+       location.setAccuracy(Taint.addTaintFloat(location.getAccuracy(), tag));
+   }    
+   // end WITH_TAINT_TRACKING
+
                         // notify other providers of the new location
                         for (int i = mProviders.size() - 1; i >= 0; i--) {
                             LocationProviderProxy proxy = mProviders.get(i);

Also, the diff of location/java/com/android/internal/location/GpsLocationProvider.java is almost the same handling as LocationManagerService.java, that is, when location updated message is received, the values are set in Taint object.

Next, I'll read the diff for media.