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/thread/Signal.h b/libs/hwui/thread/Signal.h
index d4cfeeb..93e6f4c 100644
--- a/libs/hwui/thread/Signal.h
+++ b/libs/hwui/thread/Signal.h
@@ -26,7 +26,7 @@
 
 class Signal {
 public:
-    Signal(Condition::WakeUpType type = Condition::WAKE_UP_ALL) : mType(type), mSignaled(false) { }
+    explicit Signal(Condition::WakeUpType type = Condition::WAKE_UP_ALL) : mType(type), mSignaled(false) { }
     ~Signal() { }
 
     void signal() {