Makes mus not bring window to front on activation changes

The window manager should be doing it. To do otherwise means mus is
likely conflicting with the wm. Additionally changing the activation
as we were meant clients weren't getting notified and got out of sync
with mus.

BUG=652421
TEST=covered by tests
R=msw@chromium.org

Review-Url: https://codereview.chromium.org/2391853002
Cr-Commit-Position: refs/heads/master@{#422652}

services/ui/public/cpp/window.cc

@@ -886,7 +886,6 @@ void Window::ReorderWithoutNotification(Window* window,
 }
 
 // static
-// Returns true if the order actually changed.
 bool Window::ReorderImpl(Window* window,
                          Window* relative,
                          mojom::OrderDirection direction,

services/ui/public/cpp/window.h

@@ -332,6 +332,7 @@ class Window {
   static void ReorderWithoutNotification(Window* window,
                                          Window* relative,
                                          mojom::OrderDirection direction);
+  // Returns true if the order actually changed.
   static bool ReorderImpl(Window* window,
                           Window* relative,
                           mojom::OrderDirection direction,

services/ui/ws/display.cc

@@ -351,12 +351,9 @@ bool Display::CanHaveActiveChildren(ServerWindow* window) const {
 
 void Display::OnActivationChanged(ServerWindow* old_active_window,
                                   ServerWindow* new_active_window) {
-  DCHECK_NE(new_active_window, old_active_window);
-  if (new_active_window && new_active_window->parent()) {
-    // Raise the new active window.
-    // TODO(sad): Let the WM dictate whether to raise the window or not?
-    new_active_window->parent()->StackChildAtTop(new_active_window);
-  }
+  // Don't do anything here. We assume the window manager handles restacking. If
+  // we did attempt to restack than we would have to ensure clients see the
+  // restack.
 }
 
 void Display::OnFocusChanged(FocusControllerChangeSource change_source,

services/ui/ws/window_manager_client_unittest.cc

@@ -861,15 +861,13 @@ TEST_F(WindowServerTest, Activation) {
 
   WaitForTreeSizeToMatch(parent, 6);
 
-  // |child2| and |child3| are stacked about |child1|.
-  EXPECT_GT(ValidIndexOf(parent->children(), child2),
-            ValidIndexOf(parent->children(), child1));
-  EXPECT_GT(ValidIndexOf(parent->children(), child3),
-            ValidIndexOf(parent->children(), child1));
-
-  // Set focus on |child11|. This should activate |child1|, and raise it over
-  // |child2|. But |child3| should still be above |child1| because of
-  // transiency.
+  EXPECT_EQ(0, ValidIndexOf(parent->children(), child1));
+  // NOTE: |child3| is after |child1| as |child3| is a transient child of
+  // |child1|.
+  EXPECT_EQ(1, ValidIndexOf(parent->children(), child3));
+  EXPECT_EQ(2, ValidIndexOf(parent->children(), child2));
+
+  // Set focus on |child11|, order of windows should not change.
   child11->SetFocus();
   ASSERT_TRUE(WaitForWindowToHaveFocus(child11));
   ASSERT_TRUE(WaitForWindowToHaveFocus(
@@ -878,13 +876,12 @@ TEST_F(WindowServerTest, Activation) {
             server_id(window_manager()->GetFocusedWindow()));
   EXPECT_EQ(server_id(child11), server_id(embedded1->GetFocusedWindow()));
   EXPECT_EQ(nullptr, embedded2->GetFocusedWindow());
-  EXPECT_GT(ValidIndexOf(parent->children(), child1),
-            ValidIndexOf(parent->children(), child2));
-  EXPECT_GT(ValidIndexOf(parent->children(), child3),
-            ValidIndexOf(parent->children(), child1));
+  EXPECT_EQ(0, ValidIndexOf(parent->children(), child1));
+  EXPECT_EQ(1, ValidIndexOf(parent->children(), child3));
+  EXPECT_EQ(2, ValidIndexOf(parent->children(), child2));
 
-  // Set focus on |child21|. This should activate |child2|, and raise it over
-  // |child1|.
+  // Set focus on |child21|. This should activate |child2|. Again, order should
+  // not change.
   child21->SetFocus();
   ASSERT_TRUE(WaitForWindowToHaveFocus(child21));
   ASSERT_TRUE(WaitForWindowToHaveFocus(
@@ -894,10 +891,9 @@ TEST_F(WindowServerTest, Activation) {
   EXPECT_EQ(server_id(child21), server_id(embedded2->GetFocusedWindow()));
   EXPECT_TRUE(WaitForNoWindowToHaveFocus(embedded1));
   EXPECT_EQ(nullptr, embedded1->GetFocusedWindow());
-  EXPECT_GT(ValidIndexOf(parent->children(), child2),
-            ValidIndexOf(parent->children(), child1));
-  EXPECT_GT(ValidIndexOf(parent->children(), child3),
-            ValidIndexOf(parent->children(), child1));
+  EXPECT_EQ(0, ValidIndexOf(parent->children(), child1));
+  EXPECT_EQ(1, ValidIndexOf(parent->children(), child3));
+  EXPECT_EQ(2, ValidIndexOf(parent->children(), child2));
 }
 
 TEST_F(WindowServerTest, ActivationNext) {
@@ -918,13 +914,11 @@ TEST_F(WindowServerTest, ActivationNext) {
   Window* child31 = NewVisibleWindow(GetFirstRoot(embedded3), embedded3);
   WaitForTreeSizeToMatch(parent, 7);
 
-  Window* expecteds[] = { child3, child2, child1, child3, nullptr };
   Window* focused[] = { child31, child21, child11, child31, nullptr };
-  for (size_t index = 0; expecteds[index]; ++index) {
+  for (size_t index = 0; focused[index]; ++index) {
     window_manager_client()->ActivateNextWindow();
     WaitForWindowToHaveFocus(focused[index]);
     EXPECT_TRUE(focused[index]->HasFocus());
-    EXPECT_EQ(parent->children().back(), expecteds[index]);
   }
 }