Replace non-const references by pointers

Use pointers for outputs to be consistent with the rest of
libui/libsurfaceflinger.

Remove assignFromHidlVec now that hidl_vec can be casted to std::vector.

Test: builds and boots
Change-Id: I656367028302e7b877a766eaf6aa2431fe07643b
diff --git a/include/ui/GrallocAllocator.h b/include/ui/GrallocAllocator.h
index 5645bed..dd0f9e0 100644
--- a/include/ui/GrallocAllocator.h
+++ b/include/ui/GrallocAllocator.h
@@ -47,14 +47,14 @@
 
     Error createBufferDescriptor(
             const IAllocatorClient::BufferDescriptorInfo& descriptorInfo,
-            BufferDescriptor& descriptor) const;
+            BufferDescriptor* outDescriptor) const;
     void destroyBufferDescriptor(BufferDescriptor descriptor) const;
 
-    Error allocate(BufferDescriptor descriptor, Buffer& buffer) const;
+    Error allocate(BufferDescriptor descriptor, Buffer* outBuffer) const;
     void free(Buffer buffer) const;
 
     Error exportHandle(BufferDescriptor descriptor, Buffer buffer,
-            native_handle_t*& bufferHandle) const;
+            native_handle_t** outBufferHandle) const;
 
 private:
     sp<IAllocator> mAllocator;