Add WebView API for smoothScroll

Source/web/WebViewImpl.cpp

Index: Source/web/WebViewImpl.cpp
diff --git a/Source/web/WebViewImpl.cpp b/Source/web/WebViewImpl.cpp
index 0ea604cb6c51abeec3a85071eff36d4bd5fe839b..2130358c79eff70f0bafd0534ff92cf632146b1a 100644
--- a/Source/web/WebViewImpl.cpp
+++ b/Source/web/WebViewImpl.cpp
@@ -2858,6 +2858,17 @@ bool WebViewImpl::scrollFocusedNodeIntoRect(const WebRect& rectInViewport)
     return false;
 }
 
+void WebViewImpl::smoothScroll(int targetX, int targetY, long durationMs)
+{
+    LocalFrame* frame = page()->mainFrame() && page()->mainFrame()->isLocalFrame()
+        ? page()->deprecatedLocalMainFrame() : 0;
+    if (!frame || !frame->view())
+        return;
+
+    IntPoint targetPosition(targetX, targetY);
+    startPageScaleAnimation(targetPosition, false, pageScaleFactor(), (double)durationMs / 1000);
+}
+
 void WebViewImpl::computeScaleAndScrollForFocusedNode(Node* focusedNode, bool zoomInToLegibleScale, float& newScale, IntPoint& newScroll, bool& needAnimation)
 {
     focusedNode->document().updateLayoutIgnorePendingStylesheets();