mus: Allow SetModal to fail gracefully

Mus server might prevent some windows from becoming system modals. In
this case, SetModal would fail and the client needs to handle the
failure and revert the modality set locally for the window.

BUG=548402

Review URL: https://codereview.chromium.org/1811913004

Cr-Commit-Position: refs/heads/master@{#381871}

components/mus/public/cpp/lib/in_flight_change.cc

@@ -177,6 +177,8 @@ InFlightVisibleChange::InFlightVisibleChange(Window* window,
     : InFlightChange(window, ChangeType::VISIBLE),
       revert_visible_(revert_value) {}
 
+InFlightVisibleChange::~InFlightVisibleChange() {}
+
 void InFlightVisibleChange::SetRevertValueFrom(const InFlightChange& change) {
   revert_visible_ =
       static_cast<const InFlightVisibleChange&>(change).revert_visible_;
@@ -186,4 +188,17 @@ void InFlightVisibleChange::Revert() {
   WindowPrivate(window()).LocalSetVisible(revert_visible_);
 }
 
+// InFlightSetModalChange ------------------------------------------------------
+
+InFlightSetModalChange::InFlightSetModalChange(Window* window)
+    : InFlightChange(window, ChangeType::SET_MODAL) {}
+
+InFlightSetModalChange::~InFlightSetModalChange() {}
+
+void InFlightSetModalChange::SetRevertValueFrom(const InFlightChange& change) {}
+
+void InFlightSetModalChange::Revert() {
+  WindowPrivate(window()).LocalUnsetModal();
+}
+
 }  // namespace mus

components/mus/public/cpp/lib/in_flight_change.h

@@ -253,6 +253,7 @@ class InFlightPredefinedCursorChange : public InFlightChange {
 class InFlightVisibleChange : public InFlightChange {
  public:
   InFlightVisibleChange(Window* window, const bool revert_value);
+  ~InFlightVisibleChange() override;
 
   // InFlightChange:
   void SetRevertValueFrom(const InFlightChange& change) override;
@@ -264,6 +265,19 @@ class InFlightVisibleChange : public InFlightChange {
   DISALLOW_COPY_AND_ASSIGN(InFlightVisibleChange);
 };
 
+class InFlightSetModalChange : public InFlightChange {
+ public:
+  explicit InFlightSetModalChange(Window* window);
+  ~InFlightSetModalChange() override;
+
+  // InFlightChange:
+  void SetRevertValueFrom(const InFlightChange& change) override;
+  void Revert() override;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(InFlightSetModalChange);
+};
+
 }  // namespace mus
 
 #endif  // COMPONENTS_MUS_PUBLIC_CPP_LIB_IN_FLIGHT_CHANGE_H_

components/mus/public/cpp/lib/window_private.h

@@ -62,6 +62,7 @@ class WindowPrivate {
   void LocalRemoveTransientWindow(Window* child) {
     window_->LocalRemoveTransientWindow(child);
   }
+  void LocalUnsetModal() { window_->is_modal_ = false; }
   void LocalReorder(Window* relative, mojom::OrderDirection direction) {
     window_->LocalReorder(relative, direction);
   }

components/mus/public/cpp/lib/window_tree_client_impl.cc

@@ -221,7 +221,7 @@ void WindowTreeClientImpl::RemoveTransientWindowFromParent(Window* window) {
 void WindowTreeClientImpl::SetModal(Window* window) {
   DCHECK(tree_);
   const uint32_t change_id = ScheduleInFlightChange(
-      make_scoped_ptr(new CrashInFlightChange(window, ChangeType::SET_MODAL)));
+      make_scoped_ptr(new InFlightSetModalChange(window)));
   tree_->SetModal(change_id, window->id());
 }
 

components/mus/public/cpp/tests/test_window_tree.cc

@@ -91,7 +91,10 @@ void TestWindowTree::RemoveTransientWindowFromParent(
     uint32_t change_id,
     uint32_t transient_window_id) {}
 
-void TestWindowTree::SetModal(uint32_t change_id, uint32_t window_id) {}
+void TestWindowTree::SetModal(uint32_t change_id, uint32_t window_id) {
+  got_change_ = true;
+  change_id_ = change_id;
+}
 
 void TestWindowTree::ReorderWindow(uint32_t change_id,
                                    uint32_t window_id,

components/mus/public/cpp/tests/window_tree_client_impl_unittest.cc

@@ -338,6 +338,20 @@ TEST_F(WindowTreeClientImplTest, SetVisibleFailedWithPendingChange) {
   EXPECT_EQ(original_visible, root->visible());
 }
 
+// Verifies |is_modal| is reverted if the server replied that the change failed.
+TEST_F(WindowTreeClientImplTest, SetModalFailed) {
+  WindowTreeSetup setup;
+  Window* root = setup.GetFirstRoot();
+  ASSERT_TRUE(root);
+  EXPECT_FALSE(root->is_modal());
+  root->SetModal();
+  uint32_t change_id;
+  ASSERT_TRUE(setup.window_tree()->GetAndClearChangeId(&change_id));
+  EXPECT_TRUE(root->is_modal());
+  setup.window_tree_client()->OnChangeCompleted(change_id, false);
+  EXPECT_FALSE(root->is_modal());
+}
+
 TEST_F(WindowTreeClientImplTest, InputEventBasic) {
   WindowTreeSetup setup;
   Window* root = setup.GetFirstRoot();