[OsSettingsLanguages] Disable removing last component input method

Logic is partly carried over from manage_input_methods.js

The original CL that added this logic doesn't explain much
https://crrev.com/1908483003.

This CL https://crrev.com/c/1109441 suggests component IMEs are
pre-installed system IMEs, which makes sense to ensure at least one is
enabled in case the third-party one get removed and users can no longer
type.

Button disabled view: http://screen/3qQgdYTc6UQBn8Y

Bug: 1113439
Change-Id: I4d07687a8ac0a2c705d8e83bfb938909149a2723
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2413677
Commit-Queue: My Nguyen <myy@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Reviewed-by: Regan Hsu <hsuregan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#807843}

chrome/browser/resources/settings/chromeos/os_languages_page/input_page.html

@@ -149,6 +149,8 @@
               </template>
               <div class="separator"></div>
               <cr-icon-button class="icon-clear"
+                  disabled$="[[disableRemoveInputMethod_(item,
+                      languages.inputMethods.enabled.*)]]"
                   on-click="onRemoveInputMethodClick_"
                   title="[[getRemoveInputMethodTooltip_(item)]]">
               </cr-icon-button>

chrome/browser/resources/settings/chromeos/os_languages_page/input_page.js

@@ -244,6 +244,23 @@ Polymer({
     cr.ui.focusWithoutInk(assert(this.$.addInputMethod));
   },
 
+  /**
+   * @param {!chrome.languageSettingsPrivate.InputMethod} targetInputMethod
+   * @private
+   */
+  disableRemoveInputMethod_(targetInputMethod) {
+    // Third-party IMEs can always be removed.
+    if (!this.languageHelper.isComponentIme(targetInputMethod)) {
+      return false;
+    }
+
+    // Disable remove if there is no other component IME (pre-installed
+    // system IMES) enabled.
+    return !this.languages.inputMethods.enabled.some(
+        inputMethod => inputMethod.id != targetInputMethod.id &&
+            this.languageHelper.isComponentIme(inputMethod));
+  },
+
   /**
    * @param {!chrome.languageSettingsPrivate.InputMethod} inputMethod
    * @private

chrome/test/data/webui/settings/chromeos/input_page_test.js

@@ -90,11 +90,13 @@ suite('input page', () => {
           items[0].querySelector('.display-name').textContent.trim());
       assertTrue(!!items[0].querySelector('.internal-wrapper'));
       assertFalse(!!items[0].querySelector('.external-wrapper'));
+      assertFalse(!!items[0].querySelector('.icon-clear').disabled);
       assertEquals(
           'US Dvorak keyboard',
           items[1].querySelector('.display-name').textContent.trim());
       assertTrue(!!items[1].querySelector('.external-wrapper'));
       assertFalse(!!items[1].querySelector('.internal-wrapper'));
+      assertFalse(!!items[1].querySelector('.icon-clear').disabled);
     });
 
     test('navigates to input method options page', () => {
@@ -143,6 +145,28 @@ suite('input page', () => {
           items[0].querySelector('.display-name').textContent.trim() !==
           inputMethodName);
     });
+
+    test('disables remove input method option', async () => {
+      // Add US Swahili keyboard, a third party IME
+      languageHelper.addInputMethod(
+          'ime_abcdefghijklmnopqrstuvwxyzabcdefxkb:us:sw');
+      // Remove US Dvorak keyboard, so there is only 1 component IME left.
+      languageHelper.removeInputMethod(
+          '_comp_ime_fgoepimhcoialccpbmpnnblemnepkkaoxkb:us:dvorak:eng');
+      Polymer.dom.flush();
+
+      const inputMethodsList = inputPage.$.inputMethodsList;
+      const items = inputMethodsList.querySelectorAll('.list-item');
+      assertEquals(3, items.length);
+      assertEquals(
+          'US keyboard',
+          items[0].querySelector('.display-name').textContent.trim());
+      assertTrue(!!items[0].querySelector('.icon-clear').disabled);
+      assertEquals(
+          'US Swahili keyboard',
+          items[1].querySelector('.display-name').textContent.trim());
+      assertFalse(!!items[1].querySelector('.icon-clear').disabled);
+    });
   });
 
   suite('input page', () => {
@@ -237,7 +261,7 @@ suite('input page', () => {
       assertTrue(languageHelper.isInputMethodEnabled(
           '_comp_ime_abcdefghijklmnopqrstuvwxyzabcdefxkb:sw:sw'));
       assertFalse(languageHelper.isInputMethodEnabled(
-          '_comp_ime_abcdefghijklmnopqrstuvwxyzabcdefxkb:us:sw'));
+          'ime_abcdefghijklmnopqrstuvwxyzabcdefxkb:us:sw'));
       assertTrue(languageHelper.isInputMethodEnabled(
           '_comp_ime_abcdefghijklmnopqrstuvwxyzabcdefxkb:vi:vi'));
     });

chrome/test/data/webui/settings/fake_language_settings_private.js

@@ -162,7 +162,7 @@ cr.define('settings', function() {
           enabled: false,
         },
         {
-          id: '_comp_ime_abcdefghijklmnopqrstuvwxyzabcdefxkb:us:sw',
+          id: 'ime_abcdefghijklmnopqrstuvwxyzabcdefxkb:us:sw',
           displayName: 'US Swahili keyboard',
           languageCodes: ['en', 'en-US', 'sw'],
           tags: [

chrome/test/data/webui/settings/languages_tests.js

@@ -152,7 +152,7 @@ suite('settings-languages', function() {
 
       // Add input methods for Swahili.
       const sw = '_comp_ime_abcdefghijklmnopqrstuvwxyzabcdefxkb:sw:sw';
-      const swUS = '_comp_ime_abcdefghijklmnopqrstuvwxyzabcdefxkb:us:sw';
+      const swUS = 'ime_abcdefghijklmnopqrstuvwxyzabcdefxkb:us:sw';
       languageHelper.addInputMethod(sw);
       languageHelper.addInputMethod(swUS);
       assertEquals(3, languageHelper.languages.inputMethods.enabled.length);