Release mouse pointer capture when it starts drag

third_party/WebKit/Source/platform/WebPointerEvent.cpp

Index: third_party/WebKit/Source/platform/WebPointerEvent.cpp
diff --git a/third_party/WebKit/Source/platform/WebPointerEvent.cpp b/third_party/WebKit/Source/platform/WebPointerEvent.cpp
index 21158c0b3658d464729ebae0b2b26a3cb693995b..6a4eb7f5b44c5d0799544c53914e6adf7d159ff7 100644
--- a/third_party/WebKit/Source/platform/WebPointerEvent.cpp
+++ b/third_party/WebKit/Source/platform/WebPointerEvent.cpp
@@ -27,6 +27,7 @@ WebInputEvent::Type PointerEventTypeForTouchPointState(
       return WebInputEvent::Type::kUndefined;
   }
 }
+
 }  // namespace
 
 WebPointerEvent::WebPointerEvent(const WebTouchEvent& touch_event,
@@ -50,6 +51,21 @@ WebPointerEvent::WebPointerEvent(const WebTouchEvent& touch_event,
   rotation_angle = touch_point.rotation_angle;
 }
 
+WebPointerEvent::WebPointerEvent(WebInputEvent::Type type,
+                                 const WebMouseEvent& mouse_event)
+    : WebInputEvent(sizeof(WebPointerEvent)),
+      WebPointerProperties(mouse_event),
+      width(1),
+      height(1) {
+  DCHECK_GE(type, WebInputEvent::kPointerTypeFirst);
+  DCHECK_LE(type, WebInputEvent::kPointerTypeLast);
+  SetFrameScale(mouse_event.FrameScale());
+  SetFrameTranslate(mouse_event.FrameTranslate());
+  SetTimeStampSeconds(mouse_event.TimeStampSeconds());
+  SetType(type);
+  SetModifiers(mouse_event.GetModifiers());
+}
+
 WebPointerEvent WebPointerEvent::WebPointerEventInRootFrame() const {
   WebPointerEvent transformed_event = *this;
   transformed_event.width /= frame_scale_;