Make sure constructors initialize all members

- Add default constructors to Parcelables that didn't have them and
  make sure all members are initialized by the constructors.
- Add missing fields to BufferItem flatten/unflatten.

Change-Id: I9aa83b326dc3aee757762e63be499dc96a74df91
diff --git a/include/private/gui/LayerState.h b/include/private/gui/LayerState.h
index 4b3fcc6..292dd3b 100644
--- a/include/private/gui/LayerState.h
+++ b/include/private/gui/LayerState.h
@@ -74,10 +74,10 @@
     status_t    read(const Parcel& input);
 
             struct matrix22_t {
-                float   dsdx;
-                float   dtdx;
-                float   dsdy;
-                float   dtdy;
+                float   dsdx{0};
+                float   dtdx{0};
+                float   dsdy{0};
+                float   dtdy{0};
             };
             sp<IBinder>     surface;
             uint32_t        what;