Add touchpad pinch zoom support to Blink

Source/web/WebViewImpl.h

Index: Source/web/WebViewImpl.h
diff --git a/Source/web/WebViewImpl.h b/Source/web/WebViewImpl.h
index 747446549bab51b1d4336607941acf1e19488385..4320cd71734192bdab38047bf8d79139c402f0d4 100644
--- a/Source/web/WebViewImpl.h
+++ b/Source/web/WebViewImpl.h
@@ -287,6 +287,7 @@ public:
     float defaultMaximumPageScaleFactor() const;
     float minimumPageScaleFactor() const;
     float maximumPageScaleFactor() const;
+    float clampPageScaleFactorToLimits(float) const;
 
     HitTestResult coreHitTestResultAt(const WebPoint&);
     void suppressInvalidations(bool enable);
@@ -537,7 +538,6 @@ private:
     void refreshPageScaleFactorAfterLayout();
     void resumeTreeViewCommits();
     void setUserAgentPageScaleConstraints(PageScaleConstraints newConstraints);
-    float clampPageScaleFactorToLimits(float) const;
     IntSize contentsSize() const;
 
     void updateMainFrameScrollPosition(const DoublePoint& scrollPosition, bool programmaticScroll);