Fix google-explicit-constructor warnings in gui and ui.

* Add explicit keyword to conversion constructors.
Bug: 28341362
Test: build with WITH_TIDY=1

Change-Id: I476ad1e9a4d47acb11bf4a87ad8baa855f441417
diff --git a/include/gui/IGraphicBufferProducer.h b/include/gui/IGraphicBufferProducer.h
index 37ae6df..df2b781 100644
--- a/include/gui/IGraphicBufferProducer.h
+++ b/include/gui/IGraphicBufferProducer.h
@@ -292,7 +292,7 @@
 
     struct QueueBufferInput : public Flattenable<QueueBufferInput> {
         friend class Flattenable<QueueBufferInput>;
-        inline QueueBufferInput(const Parcel& parcel);
+        explicit inline QueueBufferInput(const Parcel& parcel);
         // timestamp - a monotonically increasing value in nanoseconds
         // isAutoTimestamp - if the timestamp was synthesized at queue time
         // dataSpace - description of the contents, interpretation depends on format