Fix google-explicit-constructor warnings in frameworks/base

* Add explicit keyword to conversion constructors.
* Add NOLINT to implicit conversion constructors.

Bug: 28341362
Test: build with clang-tidy
Change-Id: Ie4d37072ab57d1662d18db4de1c8577247f43337
diff --git a/libs/hwui/SkiaCanvasProxy.h b/libs/hwui/SkiaCanvasProxy.h
index 0de9650..d8d3497 100644
--- a/libs/hwui/SkiaCanvasProxy.h
+++ b/libs/hwui/SkiaCanvasProxy.h
@@ -39,7 +39,7 @@
  */
 class ANDROID_API SkiaCanvasProxy : public SkCanvas {
 public:
-    SkiaCanvasProxy(Canvas* canvas, bool filterHwuiCalls = false);
+    explicit SkiaCanvasProxy(Canvas* canvas, bool filterHwuiCalls = false);
     virtual ~SkiaCanvasProxy() {}
 
 protected: