Fix clang-tidy warnings in libs/hwui.

* Add explicit keyword to conversion constructors.
Bug: 28341362
* Use const reference type for read-only parameters.
Bug: 30407689
Test: build with WITH_TIDY=1

Change-Id: Iab3e6636f60a70cb124f29dc19f20f842fa8dfda
Merged-In: Iab3e6636f60a70cb124f29dc19f20f842fa8dfda
diff --git a/libs/hwui/renderthread/EglManager.h b/libs/hwui/renderthread/EglManager.h
index 0a8cfd3..de932fb 100644
--- a/libs/hwui/renderthread/EglManager.h
+++ b/libs/hwui/renderthread/EglManager.h
@@ -58,7 +58,7 @@
 private:
     friend class RenderThread;
 
-    EglManager(RenderThread& thread);
+    explicit EglManager(RenderThread& thread);
     // EglContext is never destroyed, method is purposely not implemented
     ~EglManager();