GTK: when doing a drag from a web page, pass a recent mouse down to gtk_drag_begin() so it has a better idea what time to pass to gdk_grab_pointer().

I believe the following was happening:
- render view gets mouse down, forwards to webkit
- render view gets motion, forwards to webkit
- user releases mouse button, that event is added to the queue
- browser gets message from webkit that a drag has begun, calls gtk_drag_begin() with no event
- gtk_drag_begin initiates a cursor grab, but it only applies to events that have not yet been added to the queue
- mouse release comes up in queue; passed to render view rather than the drag widget

TEST=You can't get stuck in really short render view drags. Whereas it was really easy to repro before (especially in Xephyr), I can repro no longer.
BUG=http://crbug.com/15768

Review URL: http://codereview.chromium.org/150204

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@19839 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 12 insertions, 6 deletions

diff --git a/chrome/browser/tab_contents/tab_contents_view_gtk.cc b/chrome/browser/tab_contents/tab_contents_view_gtk.cc
index 84aa955..2792639 100644
--- a/chrome/browser/tab_contents/tab_contents_view_gtk.cc
+++ b/chrome/browser/tab_contents/tab_contents_view_gtk.cc
@@ -350,7 +350,7 @@ void TabContentsViewGtk::Observe(NotificationType type,
 
 void TabContentsViewGtk::ShowContextMenu(const ContextMenuParams& params) {
   context_menu_.reset(new RenderViewContextMenuGtk(tab_contents(), params,
-                                                   last_mouse_down_time_));
+                                                   last_mouse_down_.time));
   context_menu_->Init();
   context_menu_->Popup();
 }
@@ -392,7 +392,13 @@ void TabContentsViewGtk::StartDragging(const WebDropData& drop_data) {
                         0, GtkDndUtil::X_CHROME_WEBDROP_FILE_CONTENTS);
   }
 
-  gtk_drag_begin(GetContentNativeView(), list, GDK_ACTION_COPY, 1, NULL);
+  // If we don't pass an event, GDK won't know what event time to start grabbing
+  // mouse events. Technically it's the mouse motion event and not the mouse
+  // down event that causes the drag, but there's no reliable way to know
+  // *which* motion event initiated the drag, so this will have to do.
+  gtk_drag_begin(GetContentNativeView(), list, GDK_ACTION_COPY,
+                 last_mouse_down_.button,
+                 reinterpret_cast<GdkEvent*>(&last_mouse_down_));
   // The drag adds a ref; let it own the list.
   gtk_target_list_unref(list);
 }
@@ -459,7 +465,7 @@ void TabContentsViewGtk::InsertIntoContentArea(GtkWidget* widget) {
 
 gboolean TabContentsViewGtk::OnMouseDown(GtkWidget* widget,
     GdkEventButton* event, TabContentsViewGtk* view) {
-  view->last_mouse_down_time_ = event->time;
+  view->last_mouse_down_ = *event;
   return FALSE;
 }
 
diff --git a/chrome/browser/tab_contents/tab_contents_view_gtk.h b/chrome/browser/tab_contents/tab_contents_view_gtk.h
index be2b74d..b1d56d0 100644
--- a/chrome/browser/tab_contents/tab_contents_view_gtk.h
+++ b/chrome/browser/tab_contents/tab_contents_view_gtk.h
@@ -116,9 +116,9 @@ class TabContentsViewGtk : public TabContentsView,
   // between uses so that it won't go out of scope before we're done with it.
   scoped_ptr<RenderViewContextMenuGtk> context_menu_;
 
-  // The event time for the last mouse down we handled. We need this to properly
-  // show context menus.
-  guint32 last_mouse_down_time_;
+  // The event for the last mouse down we handled. We need this for context
+  // menus and drags.
+  GdkEventButton last_mouse_down_;
 
   // Used to get notifications about renderers coming and going.
   NotificationRegistrar registrar_;