Flip the IPH rectangle highlight animation

The rectangle highlight was mostly faded out, with an occasional pulse
to fade in.  The spec calls for the opposite.  Switching the animation.

BUG=724996

Review-Url: https://codereview.chromium.org/2902573002
Cr-Commit-Position: refs/heads/master@{#473961}

chrome/android/java/src/org/chromium/chrome/browser/widget/PulseDrawable.java

@@ -68,7 +68,7 @@ public class PulseDrawable extends Drawable implements Animatable {
         PulseDrawable.Painter painter = new PulseDrawable.Painter() {
             @Override
             public void modifyDrawable(PulseDrawable drawable, float interpolation) {
-                drawable.setAlpha((int) MathUtils.interpolate(12, 75, interpolation));
+                drawable.setAlpha((int) MathUtils.interpolate(12, 75, 1.f - interpolation));
             }
 
             @Override