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/thread/TaskManager.cpp b/libs/hwui/thread/TaskManager.cpp
index e9dde29..6a4587e 100644
--- a/libs/hwui/thread/TaskManager.cpp
+++ b/libs/hwui/thread/TaskManager.cpp
@@ -104,7 +104,7 @@
     return true;
 }
 
-bool TaskManager::WorkerThread::addTask(TaskWrapper task) {
+bool TaskManager::WorkerThread::addTask(const TaskWrapper& task) {
     if (!isRunning()) {
         run(mName.string(), PRIORITY_DEFAULT);
     } else if (exitPending()) {