Add new handler mechanism in MountService to make unmount api asynchronous.
MountService updates state on PackageManager and then tries to
kill processes holding file references to media about to be unmounted by
invoking api on ACtivityManager. This is retried upto 4 times to make sure all
processes holding file references are killed before unmounting the media
at specified path.

Also changed PackageManger api to return boolean value to indicate if
MountService is likely to receive broadcasts related to apps on sd.
diff --git a/services/java/com/android/server/PackageManagerService.java b/services/java/com/android/server/PackageManagerService.java
index 9e0d623..a23fac4 100644
--- a/services/java/com/android/server/PackageManagerService.java
+++ b/services/java/com/android/server/PackageManagerService.java
@@ -8877,6 +8877,9 @@
        return prefix + tmpIdx;
    }
 
+   /*
+    * Return true if PackageManager does have packages to be updated.
+    */
    public boolean updateExternalMediaStatus(final boolean mediaStatus) {
        synchronized (mPackages) {
            if (DEBUG_SD_INSTALL) Log.i(TAG, "updateExternalMediaStatus:: mediaStatus=" +
@@ -8885,16 +8888,24 @@
                return false;
            }
            mMediaMounted = mediaStatus;
-           final HashMap<SdInstallArgs, String> processCids =
-                   new HashMap<SdInstallArgs, String>();
-           final int[] uidArr = getExternalMediaPackages(mediaStatus, processCids);
-           if (processCids.size() == 0) {
+           boolean ret = false;
+           synchronized (mPackages) {
+               Set<String> appList = mSettings.findPackagesWithFlag(ApplicationInfo.FLAG_ON_SDCARD);
+               ret = appList != null && appList.size() > 0;
+           }
+           if (!ret) {
+               // No packages will be effected by the sdcard update. Just return.
                return false;
            }
             // Queue up an async operation since the package installation may take a little while.
            mHandler.post(new Runnable() {
                public void run() {
                    mHandler.removeCallbacks(this);
+                   // If we are up here that means there are packages to be
+                   // enabled or disabled.
+                   final HashMap<SdInstallArgs, String> processCids =
+                       new HashMap<SdInstallArgs, String>();
+                   final int[] uidArr = getExternalMediaPackages(mediaStatus, processCids);
                    if (mediaStatus) {
                        if (DEBUG_SD_INSTALL) Log.i(TAG, "Loading packages");
                        loadMediaPackages(processCids, uidArr);
@@ -9019,9 +9030,9 @@
            }
            args.doPostInstall(retCode);
        }
-       // Send broadcasts first
+       // Send a broadcast to let everyone know we are done processing
+       sendResourcesChangedBroadcast(true, pkgList, uidArr);
        if (pkgList.size() > 0) {
-           sendResourcesChangedBroadcast(true, pkgList, uidArr);
            Runtime.getRuntime().gc();
            // If something failed do we clean up here or next install?
        }
@@ -9049,9 +9060,9 @@
                }
            }
        }
+       sendResourcesChangedBroadcast(false, pkgList, uidArr);
        // Send broadcasts
        if (pkgList.size() > 0) {
-           sendResourcesChangedBroadcast(false, pkgList, uidArr);
            Runtime.getRuntime().gc();
        }
        // Do clean up. Just unmount