Made double-tap zoom work in pinch virtual viewport mode. (Blink-side)

public/web/WebWidget.h

Index: public/web/WebWidget.h
diff --git a/public/web/WebWidget.h b/public/web/WebWidget.h
index 5a7a80234b8aa97843930d54bc3711b4ab65a968..cd1f5de29ed9437780a6c898edcb82fd4753ba81 100644
--- a/public/web/WebWidget.h
+++ b/public/web/WebWidget.h
@@ -153,6 +153,14 @@ public:
         float scaleFactor,
         float topControlsDelta) { }
 
+    // Applies viewport related properties during a commit from the compositor
+    // thread.
+    virtual void applyViewportDeltas(
+        const WebSize& pinchViewportDelta,
+        const WebSize& mainFrameDelta,
+        float scaleFactor,
+        float topControlsDelta) { }
+
     // Called to inform the WebWidget that mouse capture was lost.
     virtual void mouseCaptureLost() { }