Fix google-explicit-constructor warnings in  opengl.

* Add explicit keyword to conversion constructors,
  or use NOLINT for implicit converters.
Bug: 28341362
Test: build with WITH_TIDY=1

Change-Id: I2508bb5c81e8fc7878a8ab5ee95cdf2c87729d85
diff --git a/opengl/libs/EGL/Loader.h b/opengl/libs/EGL/Loader.h
index 8cefe32..94f680e 100644
--- a/opengl/libs/EGL/Loader.h
+++ b/opengl/libs/EGL/Loader.h
@@ -46,7 +46,7 @@
         GLESv2      = 0x04
     };
     struct driver_t {
-        driver_t(void* gles);
+        explicit driver_t(void* gles);
         ~driver_t();
         status_t set(void* hnd, int32_t api);
         void* dso[3];
diff --git a/opengl/libs/EGL/egl_object.h b/opengl/libs/EGL/egl_object.h
index 8f3b9cb..8ceba1d 100644
--- a/opengl/libs/EGL/egl_object.h
+++ b/opengl/libs/EGL/egl_object.h
@@ -48,7 +48,7 @@
     virtual void terminate();
 
 public:
-    egl_object_t(egl_display_t* display);
+    explicit egl_object_t(egl_display_t* display);
     void destroy();
 
     inline void incRef() { count.fetch_add(1, std::memory_order_relaxed); }
@@ -63,7 +63,7 @@
     class LocalRef {
         egl_object_t* ref;
         LocalRef();
-        LocalRef(const LocalRef* rhs);
+        explicit LocalRef(const LocalRef* rhs);
     public:
         ~LocalRef();
         explicit LocalRef(egl_object_t* rhs);
diff --git a/opengl/tests/hwc/hwcTestLib.h b/opengl/tests/hwc/hwcTestLib.h
index a942c10..922fc19 100644
--- a/opengl/tests/hwc/hwcTestLib.h
+++ b/opengl/tests/hwc/hwcTestLib.h
@@ -71,7 +71,7 @@
 class ColorRGB {
   public:
     ColorRGB(): _r(0.0), _g(0.0), _b(0.0) {};
-    ColorRGB(float f): _r(f), _g(f), _b(f) {}; // Gray
+    ColorRGB(float f): _r(f), _g(f), _b(f) {}; // Gray, NOLINT(implicit)
     ColorRGB(float r, float g, float b): _r(r), _g(g), _b(b) {};
     float r(void) const { return _r; }
     float g(void) const { return _g; }