Fixes bug in dragging tabs around that could occassionally result in

the tab jumping around. The bug occurred if you dragged a tab from one
tabstrip to another, and was the result of the target tab strip not
knowing a drag is underway.

BUG=47930
TEST=see bug

Review URL: http://codereview.chromium.org/2858038

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@51296 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 27 insertions, 2 deletions

diff --git a/chrome/browser/views/tabs/base_tab_strip.cc b/chrome/browser/views/tabs/base_tab_strip.cc
index 6457d5c..316f038 100644
--- a/chrome/browser/views/tabs/base_tab_strip.cc
+++ b/chrome/browser/views/tabs/base_tab_strip.cc
@@ -430,7 +430,7 @@ void BaseTabStrip::StoppedDraggingTab(BaseTab* tab) {
 }
 
 void BaseTabStrip::PrepareForAnimation() {
-  if (!IsDragSessionActive()) {
+  if (!IsDragSessionActive() && !DraggedTabController::IsAttachedTo(this)) {
     for (int i = 0; i < tab_count(); ++i)
       base_tab_at_tab_index(i)->set_dragging(false);
   }
diff --git a/chrome/browser/views/tabs/dragged_tab_controller.cc b/chrome/browser/views/tabs/dragged_tab_controller.cc
index 7f7f7a5..18297dd 100644
--- a/chrome/browser/views/tabs/dragged_tab_controller.cc
+++ b/chrome/browser/views/tabs/dragged_tab_controller.cc
@@ -53,6 +53,9 @@ static const int kHorizontalMoveThreshold = 16;  // Pixels.
 // an attached vertical tab.
 static const int kVerticalMoveThreshold = 8;
 
+// If non-null there is a drag underway.
+static DraggedTabController* instance_;
+
 namespace {
 
 // Delay, in ms, during dragging before we bring a window to front.
@@ -341,7 +344,9 @@ DraggedTabController::DraggedTabController(BaseTab* source_tab,
       last_move_screen_loc_(0),
       mini_(source_tab->data().mini),
       pinned_(source_tabstrip->IsTabPinned(source_tab)),
-      started_drag_(false) {
+      started_drag_(false),
+      active_(true) {
+  instance_ = this;
   SetDraggedContents(
       GetModel(source_tabstrip_)->GetTabContentsAt(source_model_index_));
   // Listen for Esc key presses.
@@ -349,6 +354,9 @@ DraggedTabController::DraggedTabController(BaseTab* source_tab,
 }
 
 DraggedTabController::~DraggedTabController() {
+  if (instance_ == this)
+    instance_ = NULL;
+
   in_destructor_ = true;
   MessageLoopForUI::current()->RemoveObserver(this);
   // Need to delete the view here manually _before_ we reset the dragged
@@ -359,6 +367,12 @@ DraggedTabController::~DraggedTabController() {
   SetDraggedContents(NULL);  // This removes our observer.
 }
 
+// static
+bool DraggedTabController::IsAttachedTo(BaseTabStrip* tab_strip) {
+  return instance_ && instance_->active_ &&
+      instance_->attached_tabstrip_ == tab_strip;
+}
+
 void DraggedTabController::CaptureDragInfo(views::View* tab,
                                            const gfx::Point& mouse_offset) {
   if (tab->width() > 0) {
@@ -1045,6 +1059,8 @@ void DraggedTabController::EndDragImpl(EndDragType type) {
   // the animation finishes, this is invoked twice. The second time through
   // type == TAB_DESTROYED.
 
+  active_ = false;
+
   bring_to_front_timer_.Stop();
 
   // Hide the current dock controllers.
diff --git a/chrome/browser/views/tabs/dragged_tab_controller.h b/chrome/browser/views/tabs/dragged_tab_controller.h
index 280c3af..a860a18 100644
--- a/chrome/browser/views/tabs/dragged_tab_controller.h
+++ b/chrome/browser/views/tabs/dragged_tab_controller.h
@@ -42,6 +42,12 @@ class DraggedTabController : public TabContentsDelegate,
                        BaseTabStrip* source_tabstrip);
   virtual ~DraggedTabController();
 
+  // Returns true if there is a drag underway and the drag is attached to
+  // |tab_strip|.
+  // NOTE: this returns false if the dragged tab controller is in the process
+  // of finishing the drag.
+  static bool IsAttachedTo(BaseTabStrip* tab_strip);
+
   // Capture information needed to be used during a drag session for this
   // controller's associated source tab and BaseTabStrip. |mouse_offset| is the
   // distance of the mouse pointer from the tab's origin.
@@ -323,6 +329,9 @@ class DraggedTabController : public TabContentsDelegate,
   // Did the mouse move enough that we started a drag?
   bool started_drag_;
 
+  // Is the drag active?
+  bool active_;
+
   DISALLOW_COPY_AND_ASSIGN(DraggedTabController);
 };