[events] Allow null-named DomCodes to be mapped to/from native.

Previously NativeKeycodeToDomCode() would treat codes with a NULL name
for the DomCode (i.e. DomCodes used internally by Chrome to represent
keys with no standardized DOM |code| value.) as unknown.

This has been work-around in the DomCode table by assigning non-NULL
names to non-standard DomCodes, leading to confusion over which are
standardized mappings, and which are Chrome-internal.

Allow native keycodes with no standardized DOM |code| name to be mapped
to their Chrome-internal DomCode value, so that non-standard keys may
be switched to NULL names.

Bug: 952051
Change-Id: I1a08928765e76816410c3b005383b43910be5b51
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2020928
Commit-Queue: Navid Zolghadr <nzolghadr@chromium.org>
Reviewed-by: Navid Zolghadr <nzolghadr@chromium.org>
Reviewed-by: Dave Tapuska <dtapuska@chromium.org>
Auto-Submit: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#755499}

ui/events/keycodes/dom/keycode_converter.cc

@@ -93,10 +93,8 @@ int KeycodeConverter::InvalidNativeKeycode() {
 // static
 DomCode KeycodeConverter::NativeKeycodeToDomCode(int native_keycode) {
   for (auto& mapping : kDomCodeMappings) {
-    if (mapping.native_keycode == native_keycode) {
-      if (mapping.code != nullptr)
-        return static_cast<DomCode>(mapping.usb_keycode);
-    }
+    if (mapping.native_keycode == native_keycode)
+      return static_cast<DomCode>(mapping.usb_keycode);
   }
   return DomCode::NONE;
 }

ui/events/keycodes/dom/keycode_converter_unittest.cc

@@ -172,6 +172,10 @@ TEST(KeycodeConverter, DomCode) {
       EXPECT_STREQ(entry->code,
                    ui::KeycodeConverter::DomCodeToCodeString(code));
     }
+    ui::DomCode code =
+        ui::KeycodeConverter::NativeKeycodeToDomCode(entry->native_keycode);
+    EXPECT_EQ(entry->native_keycode,
+              ui::KeycodeConverter::DomCodeToNativeKeycode(code));
   }
 }