Check if the resizer has been deleted during drag start.

BUG=579226
TEST=ToplevelWindowEventHandler.CancelWhileDragStart

Review URL: https://codereview.chromium.org/1800793003

Cr-Commit-Position: refs/heads/master@{#381243}

3 files changed, 48 insertions, 6 deletions

diff --git a/ash/wm/dock/docked_window_resizer.cc b/ash/wm/dock/docked_window_resizer.cc
index 9e4eb2d..624dc72 100644
--- a/ash/wm/dock/docked_window_resizer.cc
+++ b/ash/wm/dock/docked_window_resizer.cc
@@ -64,17 +64,21 @@ DockedWindowResizer::Create(WindowResizer* next_window_resizer,
 void DockedWindowResizer::Drag(const gfx::Point& location, int event_flags) {
   last_location_ = location;
   ::wm::ConvertPointToScreen(GetTarget()->parent(), &last_location_);
+  base::WeakPtr<DockedWindowResizer> resizer(weak_ptr_factory_.GetWeakPtr());
+
   if (!did_move_or_resize_) {
     did_move_or_resize_ = true;
-    StartedDragging();
+    StartedDragging(resizer);
   }
+  if (!resizer)
+    return;
+
   gfx::Point offset;
   gfx::Rect bounds(CalculateBoundsForDrag(location));
   MaybeSnapToEdge(bounds, &offset);
   gfx::Point modified_location(location);
   modified_location.Offset(offset.x(), offset.y());
 
-  base::WeakPtr<DockedWindowResizer> resizer(weak_ptr_factory_.GetWeakPtr());
   next_window_resizer_->Drag(modified_location, event_flags);
   if (!resizer)
     return;
@@ -181,7 +185,8 @@ void DockedWindowResizer::MaybeSnapToEdge(const gfx::Rect& bounds,
   }
 }
 
-void DockedWindowResizer::StartedDragging() {
+void DockedWindowResizer::StartedDragging(
+    base::WeakPtr<DockedWindowResizer>& resizer) {
   // During resizing the window width is preserved by DockedwindowLayoutManager.
   if (is_docked_ &&
       (details().bounds_change & WindowResizer::kBoundsChange_Resizes)) {
@@ -192,6 +197,8 @@ void DockedWindowResizer::StartedDragging() {
   // At this point we are not yet animating the window as it may not be
   // inside the docked area.
   dock_layout_->StartDragging(GetTarget());
+  if (!resizer)
+    return;
   // Reparent workspace windows during the drag to elevate them above workspace.
   // Other windows for which the DockedWindowResizer is instantiated include
   // panels and windows that are already docked. Those do not need reparenting.
@@ -205,6 +212,8 @@ void DockedWindowResizer::StartedDragging() {
     wm::ReparentChildWithTransientChildren(GetTarget(),
                                            GetTarget()->parent(),
                                            docked_container);
+    if (!resizer)
+      return;
   }
   if (is_docked_)
     dock_layout_->DockDraggedWindow(GetTarget());
diff --git a/ash/wm/dock/docked_window_resizer.h b/ash/wm/dock/docked_window_resizer.h
index 4d5dbde..ad0e02b 100644
--- a/ash/wm/dock/docked_window_resizer.h
+++ b/ash/wm/dock/docked_window_resizer.h
@@ -54,7 +54,9 @@ class ASH_EXPORT DockedWindowResizer : public WindowResizer {
 
   // Tracks the window's initial position and attachment at the start of a drag
   // and informs the DockLayoutManager that a drag has started if necessary.
-  void StartedDragging();
+  // |resizer| can be used to check if the resizer has been deleted during
+  // StartedDragging.
+  void StartedDragging(base::WeakPtr<DockedWindowResizer>& resizer);
 
   // Informs the DockLayoutManager that the drag is complete if it was informed
   // of the drag start. |move_result| specifies if the drag was completed or
diff --git a/ash/wm/toplevel_window_event_handler_unittest.cc b/ash/wm/toplevel_window_event_handler_unittest.cc
index 55129eb..165c92c 100644
--- a/ash/wm/toplevel_window_event_handler_unittest.cc
+++ b/ash/wm/toplevel_window_event_handler_unittest.cc
@@ -17,6 +17,7 @@
 #include "base/thread_task_runner_handle.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/aura/client/aura_constants.h"
+#include "ui/aura/client/capture_client.h"
 #include "ui/aura/test/aura_test_base.h"
 #include "ui/aura/test/test_window_delegate.h"
 #include "ui/aura/window_event_dispatcher.h"
@@ -67,8 +68,8 @@ class ToplevelWindowEventHandlerTest : public AshTestBase {
     w1->SetType(ui::wm::WINDOW_TYPE_NORMAL);
     w1->set_id(1);
     w1->Init(ui::LAYER_TEXTURED);
-    aura::Window* parent = Shell::GetContainer(
-        Shell::GetPrimaryRootWindow(), kShellWindowId_AlwaysOnTopContainer);
+    aura::Window* parent = Shell::GetContainer(Shell::GetPrimaryRootWindow(),
+                                               kShellWindowId_DefaultContainer);
     parent->AddChild(w1);
     w1->SetBounds(gfx::Rect(0, 0, 100, 100));
     w1->Show();
@@ -109,6 +110,36 @@ TEST_F(ToplevelWindowEventHandlerTest, Caption) {
   EXPECT_EQ(size.ToString(), w1->bounds().size().ToString());
 }
 
+namespace {
+
+class CancelDragObserver : public aura::WindowObserver {
+ public:
+  CancelDragObserver() {}
+  ~CancelDragObserver() override {}
+
+  void OnWindowHierarchyChanging(const HierarchyChangeParams& params) override {
+    aura::client::CaptureClient* client =
+        aura::client::GetCaptureClient(params.target->GetRootWindow());
+    client->SetCapture(nullptr);
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(CancelDragObserver);
+};
+
+}  // namespace
+
+// Cancelling drag while starting window drag should not crash.
+TEST_F(ToplevelWindowEventHandlerTest, CancelWhileDragStart) {
+  scoped_ptr<aura::Window> w1(CreateWindow(HTCAPTION));
+  CancelDragObserver observer;
+  w1->AddObserver(&observer);
+  gfx::Point origin = w1->bounds().origin();
+  DragFromCenterBy(w1.get(), 100, 100);
+  EXPECT_EQ(origin, w1->bounds().origin());
+  w1->RemoveObserver(&observer);
+}
+
 TEST_F(ToplevelWindowEventHandlerTest, BottomRight) {
   scoped_ptr<aura::Window> w1(CreateWindow(HTBOTTOMRIGHT));
   gfx::Point position = w1->bounds().origin();