Fix for the continuing issues with pointer lock operations in HiDPI Chrome.

content/browser/renderer_host/render_widget_host_view_aura.cc

Index: content/browser/renderer_host/render_widget_host_view_aura.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.cc b/content/browser/renderer_host/render_widget_host_view_aura.cc
index 874e34ba3b18e6b0eec4ecc14f8562f14e81173c..00952a5278f5467c72449dffa2135da70a91c94a 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura.cc
@@ -334,6 +334,10 @@ bool PointerEventActivates(const ui::Event& event) {
   return false;
 }
 
+bool IsFractionalScaleFactor(float scale_factor) {
+  return (scale_factor - static_cast<int>(scale_factor)) > 0;
+}
+
 }  // namespace
 
 // We need to watch for mouse events outside a Web Popup or its parent
@@ -1927,6 +1931,25 @@ void RenderWidgetHostViewAura::OnMouseEvent(ui::MouseEvent* event) {
         event->type() == ui::ET_MOUSE_DRAGGED) &&
         mouse_event.x == center.x() && mouse_event.y == center.y();
 
+    // For fractional scale factors, the conversion from pixels to dip and
+    // vice versa could result in off by 1 or 2 errors which hurts us because
+    // we want to avoid sending the artificial move to center event to the
+    // renderer. Sending the move to center to the renderer cause the cursor
+    // to bounce around the center of the screen leading to the lock operation
+    // not working correctly.
+    // Workaround is to treat a mouse move or drag event off by at most 2 px
+    // from the center as a move to center event.
+    if (synthetic_move_sent_ &&
+        IsFractionalScaleFactor(current_device_scale_factor_)) {
+      if (event->type() == ui::ET_MOUSE_MOVED ||
+          event->type() == ui::ET_MOUSE_DRAGGED) {
+        if ((abs(mouse_event.x - center.x()) <= 2) &&
+            (abs(mouse_event.y - center.y()) <= 2)) {
+          is_move_to_center_event = true;
+        }
+      }
+    }
+
     ModifyEventMovementAndCoords(&mouse_event);
 
     bool should_not_forward = is_move_to_center_event && synthetic_move_sent_;