Fix google-explicit-constructor warnings in surfaceflinger.

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

Change-Id: I94f511c3be31dc22022db6466ee9ed0c6be2bc8e
diff --git a/services/surfaceflinger/DisplayHardware/FloatRect.h b/services/surfaceflinger/DisplayHardware/FloatRect.h
index 9ad1040..151eaaa 100644
--- a/services/surfaceflinger/DisplayHardware/FloatRect.h
+++ b/services/surfaceflinger/DisplayHardware/FloatRect.h
@@ -32,7 +32,7 @@
 
     inline FloatRect()
         : left(0), top(0), right(0), bottom(0) { }
-    inline FloatRect(const Rect& other)
+    inline FloatRect(const Rect& other)  // NOLINT(implicit)
         : left(other.left), top(other.top), right(other.right), bottom(other.bottom) { }
 
     inline float getWidth() const { return right - left; }