Add touchpad pinch zoom support to Blink

Source/web/WebViewImpl.cpp

Index: Source/web/WebViewImpl.cpp
diff --git a/Source/web/WebViewImpl.cpp b/Source/web/WebViewImpl.cpp
index 06e1c3efd3a9d6a137123b869811287b1502407b..26186dce3e68c3257acc877c76722f158580bf92 100644
--- a/Source/web/WebViewImpl.cpp
+++ b/Source/web/WebViewImpl.cpp
@@ -2140,8 +2140,25 @@ bool WebViewImpl::handleInputEvent(const WebInputEvent& inputEvent)
 
     // Unhandled touchpad gesture pinch events synthesize mouse wheel events.
     if (inputEvent.type == WebInputEvent::GesturePinchUpdate) {
-        if (handleSyntheticWheelFromTouchpadPinchEvent(static_cast<const WebGestureEvent&>(inputEvent)))
+        const WebGestureEvent& pinchEvent = static_cast<const WebGestureEvent&>(inputEvent);
+
+        // First, synthesize a Windows-like wheel event to send to any handlers that may exist.
+        if (handleSyntheticWheelFromTouchpadPinchEvent(pinchEvent))
             return true;
+
+        if (pinchVirtualViewportEnabled()) {
+            const float oldPageScale = pageScaleFactor();
+            const float newPageScale = clampPageScaleFactorToLimits(oldPageScale * pinchEvent.data.pinchUpdate.scale);
+            if (newPageScale != oldPageScale) {

[bokan, 2015/02/03 03:05:16]

Please fold this "changed" check inside the method.

[ccameron, 2015/02/03 17:03:28]

Done.

+                page()->frameHost().pinchViewport().setScaleAroundAnchor(
+                    newPageScale, FloatPoint(pinchEvent.x, pinchEvent.y));
+            }
+        }
+
+        // TODO(ccameron): Always return that the event was handled. Once the pinch-zoom content scale
+        // handlers have been removed from content, this function may return false if the page scale does
+        // not change.
+        return true;
     }
 
     return false;