Modified SurfaceFlinger to implment setActiveConfig and getActiveConfig.

This can be used to change the current display mode of the device.

Change-Id: Icdc3fb58389b861dc77b68102083da6f7a96eccb
Tested: None
(cherry picked from commit 2651fa94635a96d653038fb389a0dd827338f8d3)
diff --git a/services/surfaceflinger/DisplayDevice.h b/services/surfaceflinger/DisplayDevice.h
index 4c8ef02..615ca28 100644
--- a/services/surfaceflinger/DisplayDevice.h
+++ b/services/surfaceflinger/DisplayDevice.h
@@ -153,6 +153,12 @@
     void setPowerMode(int mode);
     bool isDisplayOn() const;
 
+    /* ------------------------------------------------------------------------
+     * Display active config management.
+     */
+    int getActiveConfig() const;
+    void setActiveConfig(int mode);
+
     // release HWC resources (if any) for removable displays
     void disconnect(HWComposer& hwc);
 
@@ -215,6 +221,8 @@
     bool mNeedsFiltering;
     // Current power mode
     int mPowerMode;
+    // Current active config
+    int mActiveConfig;
 };
 
 }; // namespace android