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/ProgramCache.h b/libs/hwui/ProgramCache.h
index 1dadda1..9ac885b 100644
--- a/libs/hwui/ProgramCache.h
+++ b/libs/hwui/ProgramCache.h
@@ -40,7 +40,7 @@
  */
 class ProgramCache {
 public:
-    ProgramCache(Extensions& extensions);
+    explicit ProgramCache(Extensions& extensions);
     ~ProgramCache();
 
     Program* get(const ProgramDescription& description);