SurfaceFLinger: rename outLayerId

 - Rename outId to outLayerId to reflect what the Id is.
 - Remove the default value and require it to be non-nullptr

Test: SF tests
Change-Id: Icdbbab4a84e9bd5982d274ee5bf522e36545855a
diff --git a/services/surfaceflinger/Client.h b/services/surfaceflinger/Client.h
index 9462f1a..15cd763 100644
--- a/services/surfaceflinger/Client.h
+++ b/services/surfaceflinger/Client.h
@@ -50,18 +50,18 @@
     virtual status_t createSurface(const String8& name, uint32_t w, uint32_t h, PixelFormat format,
                                    uint32_t flags, const sp<IBinder>& parent,
                                    LayerMetadata metadata, sp<IBinder>* handle,
-                                   sp<IGraphicBufferProducer>* gbp, int32_t* outId,
+                                   sp<IGraphicBufferProducer>* gbp, int32_t* outLayerId,
                                    uint32_t* outTransformHint = nullptr);
 
     virtual status_t createWithSurfaceParent(const String8& name, uint32_t w, uint32_t h,
                                              PixelFormat format, uint32_t flags,
                                              const sp<IGraphicBufferProducer>& parent,
                                              LayerMetadata metadata, sp<IBinder>* handle,
-                                             sp<IGraphicBufferProducer>* gbp, int32_t* outId,
+                                             sp<IGraphicBufferProducer>* gbp, int32_t* outLayerId,
                                              uint32_t* outTransformHint = nullptr);
 
     status_t mirrorSurface(const sp<IBinder>& mirrorFromHandle, sp<IBinder>* handle,
-                           int32_t* outId);
+                           int32_t* outLayerId);
 
     virtual status_t clearLayerFrameStats(const sp<IBinder>& handle) const;