Make drag and drop work on webpage. Also slightly modify drag drop workflow.

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 3dbf57247d50b9bdc051636cb38e5d847f663490..b15a0fd37c6f1590b80ea5b23ae2cf61c9cebe3e 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura.cc
@@ -474,6 +474,17 @@ bool RenderWidgetHostViewAura::OnMouseEvent(aura::MouseEvent* event) {
   else if (CanRendererHandleEvent(event->native_event()))
     host_->ForwardMouseEvent(content::MakeWebMouseEvent(event));
 
+  switch (event->type()) {
+    case ui::ET_MOUSE_PRESSED:
+      window_->SetCapture();
+      break;
+    case ui::ET_MOUSE_RELEASED:
+      window_->ReleaseCapture();
+      break;
+    default:
+      break;
+  }
+
   // Return true so that we receive released/drag events.
   return true;
 }