surfaceflinger: add support for gralloc dump hooks

Change-Id: Ib6f539ed0132b70d040d653c03d52cc04249ac3c
diff --git a/services/surfaceflinger/DisplayHardware/DisplayHardware.cpp b/services/surfaceflinger/DisplayHardware/DisplayHardware.cpp
index 8926c03..58751be 100644
--- a/services/surfaceflinger/DisplayHardware/DisplayHardware.cpp
+++ b/services/surfaceflinger/DisplayHardware/DisplayHardware.cpp
@@ -367,3 +367,8 @@
 {
     eglMakeCurrent(mDisplay, mSurface, mSurface, mContext);
 }
+
+void DisplayHardware::dump(String8& res) const
+{
+    mNativeWindow->dump(res);
+}