hwc: commit changes for ext display on blank

- When the device is suspended, the overlay pipes will be unset,
  but they wont be unstaged as there is no DISPLAY_COMMIT ioctl
  called for ext display, as a result the fence wont be signalled
  by the MDP.
- This is needed as we dont turn off the External display(HDMI)

Change-Id: I9794ad2ae7c9d7b4ce3f9787f50ea9da87966e41
CRs-fixed: 425483
diff --git a/libhwcomposer/hwc.cpp b/libhwcomposer/hwc.cpp
index f49ab2e..ac1be19 100644
--- a/libhwcomposer/hwc.cpp
+++ b/libhwcomposer/hwc.cpp
@@ -1,6 +1,6 @@
 /*
  * Copyright (C) 2010 The Android Open Source Project
- * Copyright (C) 2012, The Linux Foundation. All rights reserved.
+ * Copyright (C) 2012-2013, The Linux Foundation. All rights reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -233,7 +233,12 @@
             break;
         case HWC_DISPLAY_EXTERNAL:
             if(blank) {
-                //TODO actual
+                // External Display post commits the changes to display
+                // Call this on blank, so that any pipe unsets gets committed
+                if (!ctx->mExtDisplay->post()) {
+                    ret = -1;
+                    ALOGE("%s:ctx->mExtDisplay->post fail!! ", __FUNCTION__);
+                }
             } else {
             }
             break;