Fix google-explicit-constructor warnings.

Bug: 28341362
Change-Id: Ibdd6a210bb7ff228e3624cc319169f77aca3b51e
diff --git a/native/android/asset_manager.cpp b/native/android/asset_manager.cpp
index dee3f8c..0e5e5c6 100644
--- a/native/android/asset_manager.cpp
+++ b/native/android/asset_manager.cpp
@@ -39,7 +39,7 @@
     size_t mCurFileIndex;
     String8 mCachedFileName;
 
-    AAssetDir(AssetDir* dir) : mAssetDir(dir), mCurFileIndex(0) { }
+    explicit AAssetDir(AssetDir* dir) : mAssetDir(dir), mCurFileIndex(0) { }
     ~AAssetDir() { delete mAssetDir; }
 };
 
@@ -48,7 +48,7 @@
 struct AAsset {
     Asset* mAsset;
 
-    AAsset(Asset* asset) : mAsset(asset) { }
+    explicit AAsset(Asset* asset) : mAsset(asset) { }
     ~AAsset() { delete mAsset; }
 };
 
diff --git a/native/android/choreographer.cpp b/native/android/choreographer.cpp
index e35c85b..c3629da 100644
--- a/native/android/choreographer.cpp
+++ b/native/android/choreographer.cpp
@@ -64,7 +64,7 @@
     virtual ~Choreographer() = default;
 
 private:
-    Choreographer(const sp<Looper>& looper);
+    explicit Choreographer(const sp<Looper>& looper);
     Choreographer(const Choreographer&) = delete;
 
     virtual void dispatchVsync(nsecs_t timestamp, int32_t id, uint32_t count);
diff --git a/native/android/storage_manager.cpp b/native/android/storage_manager.cpp
index 399f1ff..137b72c 100644
--- a/native/android/storage_manager.cpp
+++ b/native/android/storage_manager.cpp
@@ -37,7 +37,7 @@
     sp<AStorageManager> mStorageManager;
 
 public:
-    ObbActionListener(AStorageManager* mgr) :
+    explicit ObbActionListener(AStorageManager* mgr) :
             mStorageManager(mgr)
     {}