Revise DOM Level 3 US Layout maps.

ui/events/keycodes/dom4/keycode_converter_data.h

Index: ui/events/keycodes/dom4/keycode_converter_data.h
diff --git a/ui/events/keycodes/dom4/keycode_converter_data.h b/ui/events/keycodes/dom4/keycode_converter_data.h
index 2f7712ed67b8d73cb2e0a01c599cb1b3bd0932af..3b99875a7233ea5a3c1885de36d1a0ba03f846bf 100644
--- a/ui/events/keycodes/dom4/keycode_converter_data.h
+++ b/ui/events/keycodes/dom4/keycode_converter_data.h
@@ -117,10 +117,12 @@ USB_KEYMAP_DECLARATION {
   USB_KEYMAP(0x070031, 0x0033, 0x002b, 0x002a, "Backslash", BACKSLASH),  // \|
   // USB#070032 never appears on keyboards that have USB#070031.
   // Platforms use the same scancode as for the two keys.
+  // Hence this code can only be generated synthetically
+  // (e.g. in a DOM Level 3 KeyboardEvent).
   // The keycap varies on international keyboards:
   //   Dan: '*  Dutch: <>  Ger: #'  UK: #~
   // TODO(garykac): Verify Mac intl keyboard.
-  //USB_KEYMAP(0x070032, 0x0033, 0x002b, 0x002a, "IntlHash", INTL_HASH),
+  USB_KEYMAP(0x070032, 0x0000, 0x0000, 0xffff, "IntlHash", INTL_HASH),

[Wez, 2015/05/05 00:16:00]

Ick... I forgot that the platforms are munging the USB codes for the two keys
together into the same platform-specific codes.

Note that we have a special-case for the USB-to-native code mapping (see
https://code.google.com/p/chromium/codesearch#chromium/src/ui/events/keycodes...)
to deal with this and a special-case for Mac - looks like that would be useful
for DOM-code as well, for consistency?

If we need to generate the right DOM-code strings for these platform values
we'll need an ugly special-case for these keys that generates Backslash or
IntlHash as the |code| values, dependent on the physical keyboard layout -
gross. :(

[kpschoedel, 2015/05/05 18:47:02]

Done for DomCodeToNativeKeycode() just by calling UsbKeycodeToNativeKeycode().

CodeToNativeKeycode(), which predates the enum and takes a string, is now used
only in tests, so I propose converting those and removing the function (in a
separate CL).
*Fortunately* I see no practical way to distinguish them.

   USB_KEYMAP(0x070033, 0x002f, 0x0027, 0x0029, "Semicolon", SEMICOLON),  // ;:
   USB_KEYMAP(0x070034, 0x0030, 0x0028, 0x0027, "Quote", QUOTE),      // '"
   USB_KEYMAP(0x070035, 0x0031, 0x0029, 0x0032, "Backquote", BACKQUOTE),  // `~