NOT FOR LANDING - [WebView] Allow fling animation via the LayerScrollOffsetDelegate

android_webview/java/src/org/chromium/android_webview/AwContents.java

Index: android_webview/java/src/org/chromium/android_webview/AwContents.java
diff --git a/android_webview/java/src/org/chromium/android_webview/AwContents.java b/android_webview/java/src/org/chromium/android_webview/AwContents.java
index c95137c7ec63a5d061f50cf0c56f4f90399adf86..325e6803cae5ca57d6a1ebac87ec963f82e27607 100644
--- a/android_webview/java/src/org/chromium/android_webview/AwContents.java
+++ b/android_webview/java/src/org/chromium/android_webview/AwContents.java
@@ -22,6 +22,7 @@ import android.os.Bundle;
 import android.os.Handler;
 import android.os.Message;
 import android.text.TextUtils;
+import android.util.FloatMath;
 import android.util.Log;
 import android.util.Pair;
 import android.view.KeyEvent;
@@ -31,6 +32,7 @@ import android.view.ViewGroup;
 import android.view.accessibility.AccessibilityEvent;
 import android.view.accessibility.AccessibilityNodeInfo;
 import android.view.accessibility.AccessibilityNodeProvider;
+import android.view.animation.AnimationUtils;
 import android.view.inputmethod.EditorInfo;
 import android.view.inputmethod.InputConnection;
 import android.webkit.GeolocationPermissions;
@@ -2279,14 +2281,29 @@ public class AwContents implements SmartClipProvider,
     }
 
     @CalledByNative
-    private void didOverscroll(int deltaX, int deltaY) {
+    private void didOverscroll(int deltaX, int deltaY, float velocityX, float velocityY,
+            boolean firstOverscrollX, boolean firstOverscrollY) {
         if (mOverScrollGlow != null) {
             mOverScrollGlow.setOverScrollDeltas(deltaX, deltaY);
         }
 
+        // TODO(jdduke): Skip this for components with non-zero velocity?
         mScrollOffsetManager.overScrollBy(deltaX, deltaY);
 
-        if (mOverScrollGlow != null && mOverScrollGlow.isAnimating()) {
+        if (mOverScrollGlow == null) return;
+
+        if ((velocityX != 0 && firstOverscrollX) || (velocityY != 0 && firstOverscrollY)) {
+            final int oldX = mContainerView.getScrollX();
+            final int oldY = mContainerView.getScrollY();
+            final int x = oldX + deltaX;
+            final int y = oldX + deltaY;
+            final int scrollRangeX = mScrollOffsetManager.computeMaximumHorizontalScrollOffset();
+            final int scrollRangeY = mScrollOffsetManager.computeMaximumVerticalScrollOffset();
+            mOverScrollGlow.absorbGlow(x, y, oldX, oldY, scrollRangeX, scrollRangeY,
+                    FloatMath.hypot(velocityX, velocityY));
+        }
+
+        if (mOverScrollGlow.isAnimating()) {
             postInvalidateOnAnimation();
         }
     }
@@ -2682,6 +2699,8 @@ public class AwContents implements SmartClipProvider,
 
         @Override
         public void computeScroll() {
+            if (isDestroyed()) return;
+            nativeOnComputeScroll(mNativeAwContents, AnimationUtils.currentAnimationTimeMillis());
             mScrollOffsetManager.computeScrollAndAbsorbGlow(mOverScrollGlow);
         }
     }
@@ -2719,6 +2738,8 @@ public class AwContents implements SmartClipProvider,
             long nativeAwContents, String path, ValueCallback<String> callback);
 
     private native void nativeAddVisitedLinks(long nativeAwContents, String[] visitedLinks);
+    private native void nativeOnComputeScroll(
+            long nativeAwContents, long currentAnimationTimeMillis);
     private native boolean nativeOnDraw(long nativeAwContents, Canvas canvas,
             boolean isHardwareAccelerated, int scrollX, int scrollY,
             int visibleLeft, int visibleTop, int visibleRight, int visibleBottom);