Fix google-explicit-constructor warnings.

Bug: 28341362
Change-Id: Ibdd6a210bb7ff228e3624cc319169f77aca3b51e
diff --git a/libs/hwui/SkiaCanvas.cpp b/libs/hwui/SkiaCanvas.cpp
index 644a4f3..a8e1a4b 100644
--- a/libs/hwui/SkiaCanvas.cpp
+++ b/libs/hwui/SkiaCanvas.cpp
@@ -164,7 +164,7 @@
 
 class ClipCopier : public SkCanvas::ClipVisitor {
 public:
-    ClipCopier(SkCanvas* dstCanvas) : m_dstCanvas(dstCanvas) {}
+    explicit ClipCopier(SkCanvas* dstCanvas) : m_dstCanvas(dstCanvas) {}
 
     virtual void clipRect(const SkRect& rect, SkRegion::Op op, bool antialias) {
         m_dstCanvas->clipRect(rect, op, antialias);