Make FadingEdgeScrollView more generic

chrome/android/java/src/org/chromium/chrome/browser/payments/ui/FadingEdgeScrollView.java

-// Copyright 2016 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-package org.chromium.chrome.browser.payments.ui;
-
-import android.content.Context;
-import android.graphics.Canvas;
-import android.util.AttributeSet;
-import android.widget.ScrollView;
-
-import org.chromium.chrome.R;
-import org.chromium.chrome.browser.widget.FadingShadow;
-
-/**
- * An extension of the ScrollView that supports edge shadows with alpha components.
- */
-public class FadingEdgeScrollView extends ScrollView {
-    private static final int SHADOW_COLOR = 0x11000000;
-
-    private final FadingShadow mFadingShadow;
-    private boolean mDrawTopShadow = true;
-    private boolean mDrawBottomShadow = true;
-
-    public FadingEdgeScrollView(Context context, AttributeSet attrs) {
-        super(context, attrs);
-
-        mFadingShadow = new FadingShadow(SHADOW_COLOR);
-        setFadingEdgeLength(getResources().getDimensionPixelSize(R.dimen.ntp_shadow_height));
-    }
-
-    @Override
-    protected void dispatchDraw(Canvas canvas) {
-        super.dispatchDraw(canvas);
-        setVerticalFadingEdgeEnabled(true);
-        float topShadowStrength = getTopFadingEdgeStrength();
-        float bottomShadowStrength = getBottomFadingEdgeStrength();
-        float shadowHeight = getVerticalFadingEdgeLength();
-        setVerticalFadingEdgeEnabled(false);
-
-        if (mDrawTopShadow) {
-            mFadingShadow.drawShadow(this, canvas, FadingShadow.POSITION_TOP,
-                    shadowHeight, topShadowStrength);
-        }
-
-        if (mDrawBottomShadow) {
-            mFadingShadow.drawShadow(this, canvas, FadingShadow.POSITION_BOTTOM,
-                    shadowHeight, bottomShadowStrength);
-        }
-    }
-
-    /**
-     * Sets which shadows should be drawn.
-     * @param drawTopShadow    Whether to draw the shadow on the top part of the view.
-     * @param drawBottomShadow Whether to draw the shadow on the bottom part of the view.
-     */
-    public void setShadowVisibility(boolean drawTopShadow, boolean drawBottomShadow) {
-        mDrawTopShadow = drawTopShadow;
-        mDrawBottomShadow = drawBottomShadow;
-    }
-}