Use active window if on current workspace for fullscreen mode.

ash/root_window_controller_unittest.cc

Index: ash/root_window_controller_unittest.cc
diff --git a/ash/root_window_controller_unittest.cc b/ash/root_window_controller_unittest.cc
index 9835cc5326d5d5f4178a4d93cc8776dfab00edc0..407f9b9795933b08ca19b3a52631ea42c5cce157 100644
--- a/ash/root_window_controller_unittest.cc
+++ b/ash/root_window_controller_unittest.cc
@@ -458,6 +458,44 @@ TEST_F(RootWindowControllerTest, GetWindowForFullscreenMode) {
   EXPECT_EQ(NULL, controller->GetWindowForFullscreenMode());
 }
 
+TEST_F(RootWindowControllerTest, MultipleDisplaysGetWindowForFullscreenMode) {
+  if (!SupportsMultipleDisplays())
+    return;
+
+  UpdateDisplay("600x600,600x600");
+  Shell::RootWindowControllerList controllers =
+      Shell::GetInstance()->GetAllRootWindowControllers();
+
+  Widget* w1 = CreateTestWidget(gfx::Rect(0, 0, 100, 100));
+  w1->Maximize();
+  Widget* w2 = CreateTestWidget(gfx::Rect(0, 0, 100, 100));
+  w2->SetFullscreen(true);
+  Widget* w3 = CreateTestWidget(gfx::Rect(600, 0, 100, 100));
+
+  EXPECT_EQ(w1->GetNativeWindow()->GetRootWindow(),
+      controllers[0]->root_window());
+  EXPECT_EQ(w2->GetNativeWindow()->GetRootWindow(),
+      controllers[0]->root_window());
+  EXPECT_EQ(w3->GetNativeWindow()->GetRootWindow(),
+      controllers[1]->root_window());
+
+  w1->Activate();
+  EXPECT_EQ(NULL, controllers[0]->GetWindowForFullscreenMode());
+  EXPECT_EQ(NULL, controllers[1]->GetWindowForFullscreenMode());
+
+  w2->Activate();
+  EXPECT_EQ(w2->GetNativeWindow(),
+            controllers[0]->GetWindowForFullscreenMode());
+  EXPECT_EQ(NULL, controllers[1]->GetWindowForFullscreenMode());
+
+  // Verify that the first root window controller remains in fullscreen mode
+  // when a window on the other display is activated.
+  w3->Activate();
+  EXPECT_EQ(w2->GetNativeWindow(),
+            controllers[0]->GetWindowForFullscreenMode());
+  EXPECT_EQ(NULL, controllers[1]->GetWindowForFullscreenMode());
+}
+
 // Test that user session window can't be focused if user session blocked by
 // some overlapping UI.
 TEST_F(RootWindowControllerTest, FocusBlockedWindow) {