Implement ChromeVox next/previous line, link, and heading.

chrome/browser/resources/chromeos/chromevox/manifest.json.jinja2

 {
 {%if key is defined %}
   "key": "{{key}}",
 {% endif %}
   "manifest_version": 2,
   "name": "ChromeVox",
   "version": "{{set_version}}",
   "description": "ChromeVox - Giving Voice to Chrome.",
 {% if is_guest_manifest == '1' %}
   "incognito": "split",
@@ skipping 41 matching lines @@
     "chromevox/injected/mathjax_external_util.js"
   ],
 {% if use_chromevox_next == '1' %}
   "automation": {
     "desktop": true
   },
   "commands": {
     "nextElement": {
       "description": "Moves to the next element",
       "suggested_key": {
-        "chromeos": "Search+Shift+Right"
+        "chromeos": "Search+Right"
       }
     },
     "previousElement": {
       "description": "Moves to the previous element",
       "suggested_key": {
-        "chromeos": "Search+Shift+Left"
+        "chromeos": "Search+Left"
       }
     },
     "nextLine": {
-      "description": "Moves to the next line",
+      "description": "__MSG_CHROMEVOX_NEXT_LINE__",
       "suggested_key": {
-        "chromeos": "Search+Shift+Down"
+        "chromeos": "Search+Down"
       }
     },
     "previousLine": {
-      "description": "Moves to the previous line",
+      "description": "__MSG_CHROMEVOX_PREVIOUS_LINE__",
       "suggested_key": {
-        "chromeos": "Search+Shift+Up"
+        "chromeos": "Search+Up"
+      }
+    },
+    "nextLink": {
+      "description": "__MSG_CHROMEVOX_NEXT_LINK__",
+      "suggested_key": {
+        "chromeos": "Search+L"
+      }
+    },
+    "previousLink": {
+      "description": "__MSG_CHROMEVOX_PREVIOUS_LINK__",
+      "suggested_key": {
+        "chromeos": "Search+Shift+L"
+      }
+    },
+    "nextHeading": {
+      "description": "Moves to the next heading",
+      "suggested_key": {
+        "chromeos": "Search+H"
+      }
+    },
+    "previousHeading": {
+      "description": "Moves to the previous heading",
+      "suggested_key": {
+        "chromeos": "Search+Shift+H"
       }
     }
   },
 {% endif %}
   "options_page": "chromevox/background/options.html",
   "default_locale": "en"
 }