Release mouse pointer capture when it starts drag

third_party/WebKit/Source/core/input/PointerEventManager.cpp

Index: third_party/WebKit/Source/core/input/PointerEventManager.cpp
diff --git a/third_party/WebKit/Source/core/input/PointerEventManager.cpp b/third_party/WebKit/Source/core/input/PointerEventManager.cpp
index dacc7caf55374804525a1f7d4822434b025e2306..07ca4c321313c07233dcd4f1129e9ae7da2e3e05 100644
--- a/third_party/WebKit/Source/core/input/PointerEventManager.cpp
+++ b/third_party/WebKit/Source/core/input/PointerEventManager.cpp
@@ -490,6 +490,32 @@ WebInputEventResult PointerEventManager::SendTouchPointerEvent(
   return result;
 }
 
+WebInputEventResult PointerEventManager::HandlePointerEvent(
+    const WebPointerEvent& web_pointer_event,
+    Node* target) {
+  if (web_pointer_event.GetType() == WebInputEvent::Type::kPointerCancel) {

[mustaq, 2017/07/10 16:17:30]

Nit: DCHECK for kPointerCancel instead, until we have a full-fledged EH here?

[Navid Zolghadr, 2017/07/11 15:41:06]

Done.

+    PointerEvent* pointer_event =
+        pointer_event_factory_.CreatePointerCancelEvent(web_pointer_event);
+
+    EventTarget* effective_target =
+        GetEffectiveTargetForPointerEvent(target, pointer_event->pointerId());
+    WebInputEventResult result =
+        DispatchPointerEvent(effective_target, pointer_event);
+
+    ReleasePointerCapture(pointer_event->pointerId());
+
+    // TODO(nzolghadr): Instead of |ProcessPendingPointerCapture| maybe we
+    // should have used ProcessCaptureAndPositionOfPointerEvent but that might
+    // be sending boundary events however we probably not want that all the
+    // time.
+    ProcessPendingPointerCapture(pointer_event);
+
+    RemovePointer(pointer_event);
+    return result;
+  }
+  return WebInputEventResult::kNotHandled;
+}
+
 WebInputEventResult PointerEventManager::SendMousePointerEvent(
     Node* target,
     const String& canvas_region_id,