Fix virtual display nesting

This fixes the cycling rendering loop caused by nesting virtual
displays by preventing them from recomposing if their contents
haven't changed.

Bug: 12101046
Change-Id: I600365c0fd5d3ad93e04295d26cf9de177ffc79b
diff --git a/services/surfaceflinger/DisplayHardware/FramebufferSurface.h b/services/surfaceflinger/DisplayHardware/FramebufferSurface.h
index 1d67446..ba72ce3 100644
--- a/services/surfaceflinger/DisplayHardware/FramebufferSurface.h
+++ b/services/surfaceflinger/DisplayHardware/FramebufferSurface.h
@@ -39,7 +39,7 @@
 public:
     FramebufferSurface(HWComposer& hwc, int disp, const sp<IGraphicBufferConsumer>& consumer);
 
-    virtual status_t beginFrame();
+    virtual status_t beginFrame(bool mustRecompose);
     virtual status_t prepareFrame(CompositionType compositionType);
     virtual status_t compositionComplete();
     virtual status_t advanceFrame();