MacViews: Handle three-finger swipe gestures for navigation.

ui/views/cocoa/bridged_content_view.mm

Index: ui/views/cocoa/bridged_content_view.mm
diff --git a/ui/views/cocoa/bridged_content_view.mm b/ui/views/cocoa/bridged_content_view.mm
index b47f522dd7c759f2f1450c06c5eb9b544bfe0806..b477b43db4d1e2ac9dec8a9faabf3cdcc7d62ca3 100644
--- a/ui/views/cocoa/bridged_content_view.mm
+++ b/ui/views/cocoa/bridged_content_view.mm
@@ -800,6 +800,27 @@ ui::TextEditCommand GetTextEditCommandForMenuAction(SEL action) {
   hostedView_->GetWidget()->OnScrollEvent(&event);
 }
 
+// Called when we get a three-finger swipe, and they're enabled in System
+// Preferences.
+- (void)swipeWithEvent:(NSEvent*)event {
+  if (!hostedView_)
+    return;
+
+  // We need to invert deltas in order to match GestureEventDetails's
+  // directions.
+  auto invert = [](CGFloat val) { return val * -1.; };

[tapted, 2017/02/15 22:25:53]

The comment is good, but (unless I'm missing something) the lambda isn't
necessary -- just do

ui::GestureEventDetails swipeDetails(
    ui::ET_GESTURE_SWIPE, -[event deltaX], -[event deltaY]);

[themblsha, 2017/02/16 15:27:49]

You've opened my eyes yet again. Thanks :-)

+  ui::GestureEventDetails swipeDetails(
+      ui::ET_GESTURE_SWIPE, invert([event deltaX]), invert([event deltaY]));
+  swipeDetails.set_device_type(ui::GestureDeviceType::DEVICE_TOUCHPAD);
+
+  gfx::PointF location = ui::EventLocationFromNative(event);
+  ui::GestureEvent gestureEvent(location.x(), location.y(),
+                                ui::EventFlagsFromNative(event),
+                                ui::EventTimeFromNative(event), swipeDetails);
+
+  hostedView_->GetWidget()->OnGestureEvent(&gestureEvent);
+}
+
 - (void)quickLookWithEvent:(NSEvent*)theEvent {
   if (!hostedView_)
     return;