Original issue's description:

> [DomKey] Expose Korean special keys on Korean keyboard layout only
>
> Korean keyboard has special keys "HangulMode" and "HanjaMode", we should
> only expose them when the system layout is Korean. Otherwise we should
> return "Unidentified".
>
> This matches Firefox and windows virtual key.
>
> Note: This also works with JIS keyboard + Korean layout, because we are
> mapping DomKey based on KeyboardCode instead of DomCode.
>
> BUG=612736
>
> Committed: https://crrev.com/bdcfb5a1816f1bad537d7611c7ccb972b550339c
> Cr-Commit-Position: refs/heads/master@{#399783}
> Revert: https://codereview.chromium.org/2061123005

Original issue:
Windows API |LoadKeyboardLayout()| won't pass DrMemory
tests for Korean and Japanese locale.
This should be an issue of DrMemory test or Windows itself.
See https://crbug.com/612736#c11

Solution:
Just skip |LoadKeyboardLayout()| and hardcode locale for Korean,
it works because we are only testing non-printable keys, which
doesn't care about |ToUnicodeEx()|.

Note:
|ToUnicodeEx()| returns empty string if the specified locale is invalid. (e.g. Korean HKL without calling 'LoadKeyboardLayout()')

Also Note:
"mock_keyboard.h" has the similar issue, e.g.
Call "MockKeyboard::GetCharacters(MockKeyboard::LAYOUT_KOREAN, ..)" somewhere and run DrMemory full test, which will fail as well.

BUG=612736

Review-Url: https://codereview.chromium.org/2097643002
Cr-Commit-Position: refs/heads/master@{#402611}

ui/events/keycodes/platform_key_map_win.cc

@@ -183,9 +183,6 @@ const struct NonPrintableKeyEntry {
     {VKEY_ALTGR, DomKey::ALT_GRAPH},
     {VKEY_PROCESSKEY, DomKey::PROCESS},
     // VKEY_PACKET - Used to pass Unicode char, considered as printable key.
-
-    // TODO(chongz): Handle Japanese keyboard layout keys 0xF0..0xF5.
-    // https://crbug.com/612694
     {VKEY_ATTN, DomKey::ATTN},
     {VKEY_CRSEL, DomKey::CR_SEL},
     {VKEY_EXSEL, DomKey::EX_SEL},
@@ -197,7 +194,30 @@ const struct NonPrintableKeyEntry {
     {VKEY_OEM_CLEAR, DomKey::CLEAR},
 };
 
-DomKey NonPrintableKeyboardCodeToDomKey(KeyboardCode key_code) {
+// Disambiguates the meaning of certain non-printable keys which have different
+// meanings under different languages, but use the same VKEY code.
+DomKey LanguageSpecificOemKeyboardCodeToDomKey(KeyboardCode key_code,
+                                               HKL layout) {
+  WORD language = LOWORD(layout);
+  WORD primary_language = PRIMARYLANGID(language);
+  if (primary_language == LANG_KOREAN) {
+    switch (key_code) {
+      case VKEY_HANGUL:
+        return DomKey::HANGUL_MODE;
+      case VKEY_HANJA:
+        return DomKey::HANJA_MODE;
+      default:
+        return DomKey::NONE;
+    }
+  }
+  // TODO(chongz): Handle Japanese keyboard layout keys 0xF0..0xF5, VKEY_KANA,
+  // VKEY_KANJI.
+  // https://crbug.com/612694
+  return DomKey::NONE;
+}
+
+DomKey NonPrintableKeyboardCodeToDomKey(KeyboardCode key_code, HKL layout) {
+  // 1. Most |key_codes| have the same meaning regardless of |layout|.
   const NonPrintableKeyEntry* result = std::lower_bound(
       std::begin(kNonPrintableKeyMap), std::end(kNonPrintableKeyMap), key_code,
       [](const NonPrintableKeyEntry& entry, KeyboardCode needle) {
@@ -205,7 +225,8 @@ DomKey NonPrintableKeyboardCodeToDomKey(KeyboardCode key_code) {
       });
   if (result != std::end(kNonPrintableKeyMap) && result->key_code == key_code)
     return result->dom_key;
-  return DomKey::NONE;
+  // 2. Look up a |layout|-specific meaning for |key_code|.
+  return LanguageSpecificOemKeyboardCodeToDomKey(key_code, layout);
 }
 
 void CleanupKeyMapTls(void* data) {
@@ -238,14 +259,10 @@ PlatformKeyMap::~PlatformKeyMap() {}
 
 DomKey PlatformKeyMap::DomKeyFromKeyboardCodeImpl(KeyboardCode key_code,
                                                   int flags) const {
-  DomKey key = NonPrintableKeyboardCodeToDomKey(key_code);
+  DomKey key = NonPrintableKeyboardCodeToDomKey(key_code, keyboard_layout_);
   if (key != DomKey::NONE)
     return key;
 
-  // TODO(chongz): Handle VKEY_KANA/VKEY_HANGUL, VKEY_HANJA/VKEY_KANJI based on
-  // layout.
-  // https://crbug.com/612736
-
   const int flags_to_try[] = {
       // Trying to match Firefox's behavior and UIEvents DomKey guidelines.
       // If the combination doesn't produce a printable character, the key value

ui/events/keycodes/platform_key_map_win_unittest.cc

@@ -17,8 +17,37 @@ namespace ui {
 
 namespace {
 
-const wchar_t* LAYOUT_US = L"00000409";
-const wchar_t* LAYOUT_FR = L"0000040c";
+enum Layout {
+  LAYOUT_US,
+  LAYOUT_FR,
+  LAYOUT_KR,
+};
+
+// |LoadKeyboardLayout()| ensures the locale to be loaded into the system
+// (Similar to temporarily adding a locale in Control Panel), otherwise
+// |ToUnicodeEx()| will fall-back to the default locale.
+// See MSDN LoadKeyboardLayout():
+// https://msdn.microsoft.com/en-us/library/windows/desktop/ms646305(v=vs.85).aspx
+// And language constants and strings:
+// https://msdn.microsoft.com/en-us/library/windows/desktop/dd318693(v=vs.85).aspx
+HKL GetInputLocale(Layout layout) {
+  switch (layout) {
+    case LAYOUT_US:
+      return ::LoadKeyboardLayout(L"00000409", KLF_ACTIVATE);
+    case LAYOUT_FR:
+      return ::LoadKeyboardLayout(L"0000040c", KLF_ACTIVATE);
+    case LAYOUT_KR:
+      // |LoadKeyboardLayout(L"00000412", KLF_ACTIVATE)| returns the correct
+      // Korean locale, but it will fail on DrMemory tests.
+      // See https://crbug.com/612736#c6
+      // However we could bypass it since we are only testing non-printable keys
+      // on Korean locale.
+      // (This issue only happens on Korean and Japanese).
+      return reinterpret_cast<HKL>(0x04120412);
+    default:
+      return 0;
+  }
+}
 
 struct TestKey {
   KeyboardCode key_code;
@@ -94,7 +123,7 @@ class PlatformKeyMapTest : public testing::Test {
 };
 
 TEST_F(PlatformKeyMapTest, USLayout) {
-  HKL layout = ::LoadKeyboardLayout(LAYOUT_US, 0);
+  HKL layout = GetInputLocale(LAYOUT_US);
   PlatformKeyMap keymap(layout);
 
   const TestKey kUSLayoutTestCases[] = {
@@ -143,7 +172,7 @@ TEST_F(PlatformKeyMapTest, USLayout) {
 }
 
 TEST_F(PlatformKeyMapTest, FRLayout) {
-  HKL layout = ::LoadKeyboardLayout(LAYOUT_FR, 0);
+  HKL layout = GetInputLocale(LAYOUT_FR);
   PlatformKeyMap keymap(layout);
 
   const TestKey kFRLayoutTestCases[] = {
@@ -192,7 +221,7 @@ TEST_F(PlatformKeyMapTest, FRLayout) {
 }
 
 TEST_F(PlatformKeyMapTest, NumPad) {
-  HKL layout = ::LoadKeyboardLayout(LAYOUT_US, 0);
+  HKL layout = GetInputLocale(LAYOUT_US);
   PlatformKeyMap keymap(layout);
 
   const struct TestCase {
@@ -242,7 +271,7 @@ TEST_F(PlatformKeyMapTest, NumPad) {
 }
 
 TEST_F(PlatformKeyMapTest, NonPrintableKey) {
-  HKL layout = ::LoadKeyboardLayout(LAYOUT_US, 0);
+  HKL layout = GetInputLocale(LAYOUT_US);
   PlatformKeyMap keymap(layout);
 
   for (const auto& test_case : kNonPrintableCodeMap) {
@@ -278,4 +307,31 @@ TEST_F(PlatformKeyMapTest, NonPrintableKey) {
   }
 }
 
+TEST_F(PlatformKeyMapTest, KoreanSpecificKeys) {
+  const struct TestCase {
+    KeyboardCode key_code;
+    DomKey key;
+  } kKoreanTestCases[] = {
+      {VKEY_HANGUL, DomKey::HANGUL_MODE}, {VKEY_HANJA, DomKey::HANJA_MODE},
+  };
+
+  // US English should not return values for these keys.
+  HKL us_layout = GetInputLocale(LAYOUT_US);
+  PlatformKeyMap us_keymap(us_layout);
+  for (const auto& test_case : kKoreanTestCases) {
+    EXPECT_EQ(DomKey::NONE, DomKeyFromKeyboardCodeImpl(
+                                us_keymap, test_case.key_code, EF_NONE))
+        << test_case.key_code;
+  }
+
+  // Korean layout should return specific DomKey.
+  HKL ko_layout = GetInputLocale(LAYOUT_KR);
+  PlatformKeyMap ko_keymap(ko_layout);
+  for (const auto& test_case : kKoreanTestCases) {
+    EXPECT_EQ(test_case.key, DomKeyFromKeyboardCodeImpl(
+                                 ko_keymap, test_case.key_code, EF_NONE))
+        << test_case.key_code;
+  }
+}
+
 }  // namespace ui