Bug 855975 part.3 Wrap MapVirtualKeyEx() API for converting VK to ScanCode with widget::KeyboardLayout r=jimm

widget/windows/KeyboardLayout.cpp

@@ -697,6 +697,13 @@ KeyboardLayout::IsPrintableCharKey(uint8_t aVirtualKey)
   return GetKeyIndex(aVirtualKey) >= 0;
 }
 
+WORD
+KeyboardLayout::ComputeScanCodeForVirtualKeyCode(uint8_t aVirtualKeyCode) const
+{
+  return static_cast<WORD>(
+           ::MapVirtualKeyEx(aVirtualKeyCode, MAPVK_VK_TO_VSC, GetLayout()));
+}
+
 bool
 KeyboardLayout::IsDeadKey(uint8_t aVirtualKey,
                           const ModifierKeyState& aModKeyState) const

widget/windows/KeyboardLayout.h

@@ -467,6 +467,11 @@ public:
     return mIsPendingToRestoreKeyboardLayout ? ::GetKeyboardLayout(0) :
                                                mKeyboardLayout;
   }
+
+  /**
+   * This wraps MapVirtualKeyEx() API with MAPVK_VK_TO_VSC.
+   */
+  WORD ComputeScanCodeForVirtualKeyCode(uint8_t aVirtualKeyCode) const;
 };
 
 } // namespace widget

widget/windows/nsWindow.cpp

@@ -5862,10 +5862,8 @@ nsWindow::SynthesizeNativeKeyEvent(int32_t aNativeKeyboardLayout,
     }
     ::SetKeyboardState(kbdState);
     ModifierKeyState modKeyState;
-    UINT scanCode = ::MapVirtualKeyEx(argumentKeySpecific ?
-                                        argumentKeySpecific : aNativeKeyCode,
-                                      MAPVK_VK_TO_VSC,
-                                      keyboardLayout->GetLayout());
+    UINT scanCode = keyboardLayout->ComputeScanCodeForVirtualKeyCode(
+      argumentKeySpecific ? argumentKeySpecific : aNativeKeyCode);
     LPARAM lParam = static_cast<LPARAM>(scanCode << 16);
     // Add extended key flag to the lParam for right control key and right alt
     // key.
@@ -5910,10 +5908,8 @@ nsWindow::SynthesizeNativeKeyEvent(int32_t aNativeKeyboardLayout,
     }
     ::SetKeyboardState(kbdState);
     ModifierKeyState modKeyState;
-    UINT scanCode = ::MapVirtualKeyEx(argumentKeySpecific ?
-                                        argumentKeySpecific : aNativeKeyCode,
-                                      MAPVK_VK_TO_VSC,
-                                      keyboardLayout->GetLayout());
+    UINT scanCode = keyboardLayout->ComputeScanCodeForVirtualKeyCode(
+      argumentKeySpecific ? argumentKeySpecific : aNativeKeyCode);
     LPARAM lParam = static_cast<LPARAM>(scanCode << 16);
     // Add extended key flag to the lParam for right control key and right alt
     // key.