Fix google-explicit-constructor warnings.

Bug: 28341362
Change-Id: I625fbab25f16282c2ea929cd16283d9d146fa17b
diff --git a/media/libmediaplayerservice/nuplayer/NuPlayer.cpp b/media/libmediaplayerservice/nuplayer/NuPlayer.cpp
index 36c38a2..581a671 100644
--- a/media/libmediaplayerservice/nuplayer/NuPlayer.cpp
+++ b/media/libmediaplayerservice/nuplayer/NuPlayer.cpp
@@ -69,7 +69,7 @@
 };
 
 struct NuPlayer::SeekAction : public Action {
-    SeekAction(int64_t seekTimeUs)
+    explicit SeekAction(int64_t seekTimeUs)
         : mSeekTimeUs(seekTimeUs) {
     }
 
@@ -84,7 +84,7 @@
 };
 
 struct NuPlayer::ResumeDecoderAction : public Action {
-    ResumeDecoderAction(bool needNotify)
+    explicit ResumeDecoderAction(bool needNotify)
         : mNeedNotify(needNotify) {
     }
 
@@ -99,7 +99,7 @@
 };
 
 struct NuPlayer::SetSurfaceAction : public Action {
-    SetSurfaceAction(const sp<Surface> &surface)
+    explicit SetSurfaceAction(const sp<Surface> &surface)
         : mSurface(surface) {
     }
 
@@ -131,7 +131,7 @@
 };
 
 struct NuPlayer::PostMessageAction : public Action {
-    PostMessageAction(const sp<AMessage> &msg)
+    explicit PostMessageAction(const sp<AMessage> &msg)
         : mMessage(msg) {
     }
 
@@ -150,7 +150,7 @@
 struct NuPlayer::SimpleAction : public Action {
     typedef void (NuPlayer::*ActionFunc)();
 
-    SimpleAction(ActionFunc func)
+    explicit SimpleAction(ActionFunc func)
         : mFunc(func) {
     }