Fix bug that Capslock is triggered unintendedly

Modify the function CanHandleToggleCapsLock: pressing any
redundant key will prevent triggering the Capslock shortcut.

In original code, pressing Alt + M + Search then releasing Alt
will trigger CapsLock. Because AcceleratorHistory will receive
Alt + Search when Search is pressed. The fact that key M is pr-
-essed is ignored.

R=afakhry@chromium.org

Bug: 789283
Test: ash unittests
Change-Id: Id359d11cda4562a0b90da97af6c3dde3faf33c53
Reviewed-on: https://chromium-review.googlesource.com/1199853
Commit-Queue: Andrew Xu <andrewxu@chromium.org>
Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Cr-Commit-Position: refs/heads/master@{#589702}

ash/accelerators/accelerator_controller.cc

@@ -752,8 +752,18 @@ void HandleCycleUser(CycleUserDirection direction) {
   Shell::Get()->session_controller()->CycleActiveUser(direction);
 }
 
-bool CanHandleToggleCapsLock(const ui::Accelerator& accelerator,
-                             const ui::Accelerator& previous_accelerator) {
+bool CanHandleToggleCapsLock(
+    const ui::Accelerator& accelerator,
+    const ui::Accelerator& previous_accelerator,
+    const std::set<ui::KeyboardCode>& currently_pressed_keys) {
+  // Iterate the set of pressed keys. If any redundant key is pressed, CapsLock
+  // should not be triggered. Otherwise, CapsLock may be triggered accidentally.
+  // See issue 789283 (https://crbug.com/789283)
+  for (const auto& pressed_key : currently_pressed_keys) {
+    if (pressed_key != ui::VKEY_LWIN && pressed_key != ui::VKEY_MENU)
+      return false;
+  }
+
   // This shortcust is set to be trigger on release. Either the current
   // accelerator is a Search release or Alt release.
   if (accelerator.key_code() == ui::VKEY_LWIN &&
@@ -1309,7 +1319,9 @@ bool AcceleratorController::CanPerformAction(
     case TOGGLE_APP_LIST:
       return CanHandleToggleAppList(accelerator, previous_accelerator);
     case TOGGLE_CAPS_LOCK:
-      return CanHandleToggleCapsLock(accelerator, previous_accelerator);
+      return CanHandleToggleCapsLock(
+          accelerator, previous_accelerator,
+          accelerator_history_->currently_pressed_keys());
     case TOGGLE_DICTATION:
       return CanHandleToggleDictation();
     case TOGGLE_DOCKED_MAGNIFIER:

ash/accelerators/accelerator_controller_unittest.cc

@@ -975,6 +975,17 @@ TEST_F(AcceleratorControllerTest, ToggleCapsLockAccelerators) {
   EXPECT_EQ(4, client.set_caps_lock_count_);
   EXPECT_TRUE(controller->IsCapsLockEnabled());
   controller->UpdateCapsLockState(false);
+
+  // 5. Press M, Press Alt, Press Search, Release Alt. After that CapsLock
+  // should not be triggered. https://crbug.com/789283
+  ui::test::EventGenerator* generator = GetEventGenerator();
+  generator->PressKey(ui::VKEY_M, ui::EF_NONE);
+  generator->PressKey(ui::VKEY_MENU, ui::EF_NONE);
+  generator->PressKey(ui::VKEY_LWIN, ui::EF_ALT_DOWN);
+  generator->ReleaseKey(ui::VKEY_MENU, ui::EF_COMMAND_DOWN);
+  controller->FlushMojoForTesting();
+  EXPECT_FALSE(controller->IsCapsLockEnabled());
+  controller->UpdateCapsLockState(false);
 }
 
 class PreferredReservedAcceleratorsTest : public AshTestBase {

ui/base/accelerators/accelerator_history.h

@@ -31,6 +31,10 @@ class UI_BASE_EXPORT AcceleratorHistory {
     return previous_accelerator_;
   }
 
+  const std::set<KeyboardCode>& currently_pressed_keys() const {
+    return currently_pressed_keys_;
+  }
+
   // Stores the given |accelerator| only if it's different than the currently
   // stored one.
   void StoreCurrentAccelerator(const Accelerator& accelerator);