[chromecast] Fix backspace & delete in virtual keyboard

  * Backspace, tab, and delete are special in that they are characters,
    but non-printable.
  * This catches them and passes them through as non-printable class
    characters, so they are properly handled by blink.

Bug: internal b/174869138
Test: manual with wayland_webview_client
Change-Id: I2e33c602fbe6c85f0998717541d2f5fca0b48a5f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2625207Reviewed-by: Kevin Schoedel <kpschoedel@chromium.org>
Reviewed-by: Shawn Gallea <sagallea@google.com>
Reviewed-by: Daniel Nicoara <dnicoara@chromium.org>
Commit-Queue: Ryan Daum <rdaum@chromium.org>
Cr-Commit-Position: refs/heads/master@{#842678}

chromecast/browser/webview/web_content_controller.cc

@@ -338,17 +338,24 @@ void WebContentController::ProcessInputEvent(const webview::InputEvent& ev) {
       if (ev.has_key()) {
         ui::DomKey dom_key =
             ui::KeycodeConverter::KeyStringToDomKey(ev.key().key_string());
-        bool is_char = dom_key.IsCharacter();
-        int32_t key_code = is_char ? dom_key.ToCharacter()
-                                   : NonPrintableDomKeyToKeyboardCode(dom_key);
+
+        // Backspace, delete, and tab have to be treated specially as they are
+        // characters according to DomKey, but they are non-printable.
+        bool is_printable_character =
+            dom_key.IsCharacter() && dom_key != ui::DomKey::TAB &&
+            dom_key != ui::DomKey::BACKSPACE && dom_key != ui::DomKey::DEL;
+
         ui::KeyboardCode keyboard_code =
-            static_cast<ui::KeyboardCode>(key_code);
+            is_printable_character
+                ? static_cast<ui::KeyboardCode>(dom_key.ToCharacter())
+                : NonPrintableDomKeyToKeyboardCode(dom_key);
         ui::KeyEvent evt(type, keyboard_code,
                          UsLayoutKeyboardCodeToDomCode(keyboard_code),
                          ev.flags() | ui::EF_IS_SYNTHESIZED, dom_key,
                          base::TimeTicks() +
                              base::TimeDelta::FromMicroseconds(ev.timestamp()),
-                         is_char);
+                         is_printable_character);
+
         // Marks the simulated key event is from a Virtual Keyboard.
         ui::Event::Properties properties;
         properties[ui::kPropertyFromVK] =