Fix 1997929. The final mScrollX/Y has been pinned to the legal bounds.

So we can't use it to calculate the intermediate scroll position. Use
the original scroll offset and scale to find the animated scroll position.

core/java/android/webkit/WebView.java

@@ -531,6 +531,8 @@ public class WebView extends AbsoluteLayout
     private float mZoomScale;
     private float mInvInitialZoomScale;
     private float mInvFinalZoomScale;
+    private int mInitialScrollX;
+    private int mInitialScrollY;
     private long mZoomStart;
     private static final int ZOOM_ANIMATION_LENGTH = 500;
 
@@ -2558,24 +2560,15 @@ public class WebView extends AbsoluteLayout
                 // set mZoomScale to be 0 as we have done animation
                 mZoomScale = 0;
             }
-            float scale = (mActualScale - zoomScale) * mInvActualScale;
-            float tx = scale * (mZoomCenterX + mScrollX);
-            float ty = scale * (mZoomCenterY + mScrollY);
-
-            // this block pins the translate to "legal" bounds. This makes the
-            // animation a bit non-obvious, but it means we won't pop when the
-            // "real" zoom takes effect
-            if (true) {
-               // canvas.translate(mScrollX, mScrollY);
-                tx -= mScrollX;
-                ty -= mScrollY;
-                tx = -pinLoc(-Math.round(tx), getViewWidth(), Math
-                        .round(mContentWidth * zoomScale));
-                ty = -pinLoc(-Math.round(ty), getViewHeight(), Math
-                        .round(mContentHeight * zoomScale));
-                tx += mScrollX;
-                ty += mScrollY;
-            }
+            float scale = zoomScale * mInvInitialZoomScale;
+            int tx = Math.round(scale * (mInitialScrollX + mZoomCenterX)
+                    - mZoomCenterX);
+            tx = -pinLoc(tx, getViewWidth(), Math.round(mContentWidth
+                    * zoomScale)) + mScrollX;
+            int ty = Math.round(scale * (mInitialScrollY + mZoomCenterY)
+                    - mZoomCenterY);
+            ty = -pinLoc(ty, getViewHeight(), Math.round(mContentHeight
+                    * zoomScale)) + mScrollY;
             canvas.translate(tx, ty);
             canvas.scale(zoomScale, zoomScale);
         } else {
@@ -4350,6 +4343,8 @@ public class WebView extends AbsoluteLayout
 
     private boolean zoomWithPreview(float scale) {
         float oldScale = mActualScale;
+        mInitialScrollX = mScrollX;
+        mInitialScrollY = mScrollY;
 
         // snap to DEFAULT_SCALE if it is close
         if (scale > (mDefaultScale - 0.05) && scale < (mDefaultScale + 0.05)) {