Force a repaint when hwc invalidate hook is called

without this prepare() would be called but not set() since the
dirty region is empty.

Change-Id: I038acfbdad4c16015357ccde4d1949391d6f989d
diff --git a/services/surfaceflinger/DisplayHardware/HWComposer.cpp b/services/surfaceflinger/DisplayHardware/HWComposer.cpp
index 879e858..be9b226 100644
--- a/services/surfaceflinger/DisplayHardware/HWComposer.cpp
+++ b/services/surfaceflinger/DisplayHardware/HWComposer.cpp
@@ -75,7 +75,7 @@
 }
 
 void HWComposer::invalidate() {
-    mFlinger->signalEvent();
+    mFlinger->repaintEverything();
 }
 
 void HWComposer::setFrameBuffer(EGLDisplay dpy, EGLSurface sur) {
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index 43191b7..128a64d 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -256,12 +256,11 @@
 public:     // hack to work around gcc 4.0.3 bug
     const GraphicPlane&     graphicPlane(int dpy) const;
           GraphicPlane&     graphicPlane(int dpy);
-private:
+          void              signalEvent();
+          void              repaintEverything();
 
-            void        waitForEvent();
-public:     // hack to work around gcc 4.0.3 bug
-            void        signalEvent();
 private:
+            void        waitForEvent();
             void        handleConsoleEvents();
             void        handleTransaction(uint32_t transactionFlags);
             void        handleTransactionLocked(uint32_t transactionFlags);
@@ -279,7 +278,6 @@
             void        postFramebuffer();
             void        setupHardwareComposer(Region& dirtyInOut);
             void        composeSurfaces(const Region& dirty);
-            void        repaintEverything();
 
 
             ssize_t     addClientLayer(const sp<Client>& client,