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/PathCache.h b/libs/hwui/PathCache.h
index c529915..86c59b5 100644
--- a/libs/hwui/PathCache.h
+++ b/libs/hwui/PathCache.h
@@ -290,7 +290,7 @@
 
     class PathProcessor: public TaskProcessor<SkBitmap*> {
     public:
-        PathProcessor(Caches& caches);
+        explicit PathProcessor(Caches& caches);
         ~PathProcessor() { }
 
         virtual void onProcess(const sp<Task<SkBitmap*> >& task) override;