[Android] Add slack to allow refresh after overscrolling

content/browser/android/overscroll_glow.h

Index: content/browser/android/overscroll_glow.h
diff --git a/content/browser/android/overscroll_glow.h b/content/browser/android/overscroll_glow.h
index 8685c9c788609ee43a2afdc02f2df2b9882a706c..80a1b106cf4ace93b5ea0a5dcc3ef5e45e43190c 100644
--- a/content/browser/android/overscroll_glow.h
+++ b/content/browser/android/overscroll_glow.h
@@ -69,6 +69,10 @@ class OverscrollGlow {
   // Whether the effect is active, either being pulled or receding.
   bool IsActive() const;
 
+  // The maximum alpha value (in the range [0,1]) of any animated edge layers.
+  // If the effect is inactive, this will be 0.
+  float GetVisibleAlpha() const;
+
  private:
   enum Axis { AXIS_X, AXIS_Y };