Fix google-explicit-constructor warnings in libs/hwui.

* Add explicit keyword to conversion constructors,
  or add NOLINT for implicit converters.
Bug: 28341362
Test: build with WITH_TIDY=1

Change-Id: Id8ca42433a4fc3652e4cb13787c4cb169f20d9a9
diff --git a/libs/hwui/DeferredLayerUpdater.h b/libs/hwui/DeferredLayerUpdater.h
index 44a24c8..4005822 100644
--- a/libs/hwui/DeferredLayerUpdater.h
+++ b/libs/hwui/DeferredLayerUpdater.h
@@ -35,7 +35,7 @@
 public:
     // Note that DeferredLayerUpdater assumes it is taking ownership of the layer
     // and will not call incrementRef on it as a result.
-    ANDROID_API DeferredLayerUpdater(Layer* layer);
+    ANDROID_API explicit DeferredLayerUpdater(Layer* layer);
     ANDROID_API ~DeferredLayerUpdater();
 
     ANDROID_API bool setSize(int width, int height) {