Invoke a padding round in certain use-cases.

* In some use-cases, it is possible that there are
no AppBuffer layers on the external/virtual layer-list
during which all the pipes will be allocated to the
primary. When layers do comeup on external/virtual
layer-list, subsequent overlay sets fail.

* This change ensures that in such cases, we invoke a
padding round on all the displays to free up the
hw resources which can be used in subsequent cycles.

Change-Id: Ifac0b8f51a8719eb55b11010d05b8d11352db054
diff --git a/libhwcomposer/hwc.cpp b/libhwcomposer/hwc.cpp
index 5c9f2d1..80e7803 100644
--- a/libhwcomposer/hwc.cpp
+++ b/libhwcomposer/hwc.cpp
@@ -105,7 +105,10 @@
 //Helper
 static void reset(hwc_context_t *ctx, int numDisplays,
                   hwc_display_contents_1_t** displays) {
+
     ctx->numActiveDisplays = 0;
+    ctx->isPaddingRound = false;
+
     for(int i = 0; i < numDisplays; i++) {
         hwc_display_contents_1_t *list = displays[i];
         // XXX:SurfaceFlinger no longer guarantees that this
@@ -125,6 +128,17 @@
              * the display device to be active.
              */
             ctx->numActiveDisplays += 1;
+
+            if((ctx->mPrevHwLayerCount[i] == 1) and (list->numHwLayers > 1)) {
+                /* If the previous cycle for dpy 'i' has 0 AppLayers and the
+                 * current cycle has atleast 1 AppLayer, padding round needs
+                 * to be invoked on current cycle to free up the resources.
+                 */
+                ctx->isPaddingRound = true;
+            }
+            ctx->mPrevHwLayerCount[i] = list->numHwLayers;
+        } else {
+            ctx->mPrevHwLayerCount[i] = 0;
         }
 
         if(ctx->mFBUpdate[i])
@@ -133,7 +147,6 @@
             ctx->mCopyBit[i]->reset();
         if(ctx->mLayerRotMap[i])
             ctx->mLayerRotMap[i]->reset();
-
     }
 
     ctx->mAD->reset();