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/DisplayHardware/HWComposer.h b/services/surfaceflinger/DisplayHardware/HWComposer.h
index 9bd99eb..5cb56a0 100644
--- a/services/surfaceflinger/DisplayHardware/HWComposer.h
+++ b/services/surfaceflinger/DisplayHardware/HWComposer.h
@@ -100,6 +100,9 @@
     // set power mode
     status_t setPowerMode(int disp, int mode);
 
+    // set active config
+    status_t setActiveConfig(int disp, int mode);
+
     // reset state when an external, non-virtual display is disconnected
     void disconnectDisplay(int disp);