Fix google-explicit-constructor warnings in camera.

* Add explicit keyword to conversion constructors.
Bug: 28341362
Test: build with WITH_TIDY=1

Change-Id: I61f9b5b2b6e13e0c6561327bc8dfe69c9cfc5ba5
diff --git a/camera/ndk/impl/ACameraCaptureSession.h b/camera/ndk/impl/ACameraCaptureSession.h
index 58428e6..f56219c 100644
--- a/camera/ndk/impl/ACameraCaptureSession.h
+++ b/camera/ndk/impl/ACameraCaptureSession.h
@@ -24,7 +24,7 @@
 using namespace android;
 
 struct ACaptureSessionOutput {
-    ACaptureSessionOutput(ANativeWindow* window) : mWindow(window) {};
+    explicit ACaptureSessionOutput(ANativeWindow* window) : mWindow(window) {};
 
     bool operator == (const ACaptureSessionOutput& other) const {
         return mWindow == other.mWindow;