Fix clang-tidy warnings in libs/hwui.

* Add explicit keyword to conversion constructors.
Bug: 28341362
* Use const reference type for read-only parameters.
Bug: 30407689
Test: build with WITH_TIDY=1

Change-Id: Iab3e6636f60a70cb124f29dc19f20f842fa8dfda
diff --git a/libs/hwui/Interpolator.h b/libs/hwui/Interpolator.h
index 66ce119..6512008 100644
--- a/libs/hwui/Interpolator.h
+++ b/libs/hwui/Interpolator.h
@@ -43,7 +43,7 @@
 
 class ANDROID_API AccelerateInterpolator : public Interpolator {
 public:
-    AccelerateInterpolator(float factor) : mFactor(factor), mDoubleFactor(factor*2) {}
+    explicit AccelerateInterpolator(float factor) : mFactor(factor), mDoubleFactor(factor*2) {}
     virtual float interpolate(float input) override;
 private:
     const float mFactor;
@@ -52,7 +52,7 @@
 
 class ANDROID_API AnticipateInterpolator : public Interpolator {
 public:
-    AnticipateInterpolator(float tension) : mTension(tension) {}
+    explicit AnticipateInterpolator(float tension) : mTension(tension) {}
     virtual float interpolate(float input) override;
 private:
     const float mTension;
@@ -60,7 +60,7 @@
 
 class ANDROID_API AnticipateOvershootInterpolator : public Interpolator {
 public:
-    AnticipateOvershootInterpolator(float tension) : mTension(tension) {}
+    explicit AnticipateOvershootInterpolator(float tension) : mTension(tension) {}
     virtual float interpolate(float input) override;
 private:
     const float mTension;
@@ -73,7 +73,7 @@
 
 class ANDROID_API CycleInterpolator : public Interpolator {
 public:
-    CycleInterpolator(float cycles) : mCycles(cycles) {}
+    explicit CycleInterpolator(float cycles) : mCycles(cycles) {}
     virtual float interpolate(float input) override;
 private:
     const float mCycles;
@@ -81,7 +81,7 @@
 
 class ANDROID_API DecelerateInterpolator : public Interpolator {
 public:
-    DecelerateInterpolator(float factor) : mFactor(factor) {}
+    explicit DecelerateInterpolator(float factor) : mFactor(factor) {}
     virtual float interpolate(float input) override;
 private:
     const float mFactor;
@@ -94,7 +94,7 @@
 
 class ANDROID_API OvershootInterpolator : public Interpolator {
 public:
-    OvershootInterpolator(float tension) : mTension(tension) {}
+    explicit OvershootInterpolator(float tension) : mTension(tension) {}
     virtual float interpolate(float input) override;
 private:
     const float mTension;