Add getBufferCount API to Overlay objects

Signed-off-by: Rebecca Schultz Zavin <rebecca@android.com>

include/ui/Overlay.h

@@ -91,6 +91,7 @@ public:
     int32_t getFormat() const;
     int32_t getWidthStride() const;
     int32_t getHeightStride() const;
+    int32_t getBufferCount() const;
     status_t getStatus() const;
     
 private:

libs/ui/Overlay.cpp

@@ -59,6 +59,12 @@ status_t Overlay::queueBuffer(overlay_buffer_t buffer)
     return mOverlayData->queueBuffer(mOverlayData, buffer);
 }
 
+int32_t Overlay::getBufferCount() const
+{
+    if (mStatus != NO_ERROR) return mStatus;
+    return mOverlayData->getBufferCount(mOverlayData);
+}
+
 void* Overlay::getBufferAddress(overlay_buffer_t buffer)
 {
     if (mStatus != NO_ERROR) return NULL;