Fix the issue of cursor's device scale factor when using monitors with differnt device scale factor.

chrome/browser/ui/views/tabs/tab_drag_controller_interactive_uitest.cc

Index: chrome/browser/ui/views/tabs/tab_drag_controller_interactive_uitest.cc
diff --git a/chrome/browser/ui/views/tabs/tab_drag_controller_interactive_uitest.cc b/chrome/browser/ui/views/tabs/tab_drag_controller_interactive_uitest.cc
index 190f5edb44dbb4ac5e808739cd052ce8e465be13..b59d82c632333787029ebce69a21c5252434a223 100644
--- a/chrome/browser/ui/views/tabs/tab_drag_controller_interactive_uitest.cc
+++ b/chrome/browser/ui/views/tabs/tab_drag_controller_interactive_uitest.cc
@@ -36,6 +36,8 @@
 #include "ash/display/display_controller.h"
 #include "ash/display/multi_display_manager.h"
 #include "ash/shell.h"
+#include "ash/test/cursor_manager_test_api.h"
+#include "ash/wm/cursor_manager.h"
 #include "ui/aura/test/event_generator.h"
 #include "ui/aura/root_window.h"
 #endif
@@ -1115,6 +1117,103 @@ IN_PROC_BROWSER_TEST_P(DetachToBrowserInSeparateDisplayTabDragControllerTest,
   EXPECT_EQ("1", IDString(browser()->tab_strip_model()));
 }
 
+class DifferentDeviceScaleFactorDisplayTabDragControllerTest
+    : public DetachToBrowserTabDragControllerTest {
+ public:
+  DifferentDeviceScaleFactorDisplayTabDragControllerTest() {}
+
+  virtual void SetUpCommandLine(CommandLine* command_line) OVERRIDE {
+    DetachToBrowserTabDragControllerTest::SetUpCommandLine(command_line);
+    command_line->AppendSwitchASCII("aura-host-window-size",
+                                    "400x400,800x800*2");
+  }
+
+  float GetCursorDeviceScaleFactor() const {
+    ash::test::CursorManagerTestApi cursor_test_api(
+        ash::Shell::GetInstance()->cursor_manager());
+    return cursor_test_api.GetDeviceScaleFactor();
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(
+      DifferentDeviceScaleFactorDisplayTabDragControllerTest);
+};
+
+namespace {
+
+// The points where a tab is dragged in CursorDeviceScaleFactorStep.
+const struct DragPoint {
+  int x;
+  int y;
+} kDragPoints[] = {
+  {300, 200},
+  {399, 200},
+  {500, 200},
+  {400, 200},
+  {300, 200},
+};
+
+// The expected device scale factors before the cursor is moved to the
+// corresponding kDragPoints in CursorDeviceScaleFactorStep.
+const float kDeviceScaleFactorExpectations[] = {
+  1.0f,
+  1.0f,
+  2.0f,
+  2.0f,
+  1.0f,
+};
+
+COMPILE_ASSERT(
+    arraysize(kDragPoints) == arraysize(kDeviceScaleFactorExpectations),
+    kDragPoints_and_kDeviceScaleFactorExpectations_must_have_same_size);
+
+// Drags tab to |kDragPoints[index]|, then calls the next step function.
+void CursorDeviceScaleFactorStep(
+    DifferentDeviceScaleFactorDisplayTabDragControllerTest* test,
+    TabStrip* not_attached_tab_strip,
+    size_t index) {
+  ASSERT_FALSE(not_attached_tab_strip->IsDragSessionActive());
+  ASSERT_TRUE(TabDragController::IsActive());
+
+  if (index < arraysize(kDragPoints)) {
+    EXPECT_EQ(kDeviceScaleFactorExpectations[index],
+              test->GetCursorDeviceScaleFactor());
+    const DragPoint p = kDragPoints[index];
+    ASSERT_TRUE(test->DragInputToNotifyWhenDone(
+        p.x, p.y, base::Bind(&CursorDeviceScaleFactorStep,
+                             test, not_attached_tab_strip, index + 1)));
+  } else {
+    // Finishes a serise of CursorDeviceScaleFactorStep calls and ends drag.
+    EXPECT_EQ(1.0f, test->GetCursorDeviceScaleFactor());
+    ASSERT_TRUE(ui_test_utils::SendMouseEventsSync(
+        ui_controls::LEFT, ui_controls::UP));
+  }
+}
+
+}  // namespace
+
+// Verifies cursor's device scale factor is updated when a tab is moved across
+// displays with different device scale factors (http://crbug.com/154183).
+IN_PROC_BROWSER_TEST_P(DifferentDeviceScaleFactorDisplayTabDragControllerTest,
+                       CursorDeviceScaleFactor) {
+  // Add another tab.
+  AddTabAndResetBrowser(browser());
+  TabStrip* tab_strip = GetTabStripForBrowser(browser());
+
+  // Move the second browser to the second display.
+  std::vector<aura::RootWindow*> roots(ash::Shell::GetAllRootWindows());
+  ASSERT_EQ(2u, roots.size());
+
+  // Move to the first tab and drag it enough so that it detaches.
+  gfx::Point tab_0_center(GetCenterInScreenCoordinates(tab_strip->tab_at(0)));
+  ASSERT_TRUE(PressInput(tab_0_center));
+  ASSERT_TRUE(DragInputToNotifyWhenDone(
+                  tab_0_center.x(), tab_0_center.y() + GetDetachY(tab_strip),
+                  base::Bind(&CursorDeviceScaleFactorStep,
+                             this, tab_strip, 0)));
+  QuitWhenNotDragging();
+}
+
 namespace {
 
 class DetachToBrowserInSeparateDisplayAndCancelTabDragControllerTest
@@ -1271,6 +1370,9 @@ INSTANTIATE_TEST_CASE_P(TabDragging,
                         DetachToBrowserInSeparateDisplayTabDragControllerTest,
                         ::testing::Values("mouse", "touch"));
 INSTANTIATE_TEST_CASE_P(TabDragging,
+                        DifferentDeviceScaleFactorDisplayTabDragControllerTest,
+                        ::testing::Values("mouse"));
+INSTANTIATE_TEST_CASE_P(TabDragging,
                         DetachToBrowserTabDragControllerTest,
                         ::testing::Values("mouse", "touch"));
 #else