First pass at experimental omnibox API. There are plenty of rough edges and

chrome/common/extensions/extension.cc

Index: chrome/common/extensions/extension.cc
diff --git a/chrome/common/extensions/extension.cc b/chrome/common/extensions/extension.cc
index 89d709573be6b3d6d5d119830eb1b96a9f2e1af9..f68445e14b3b8b7f9b4443d11cd1616ec9a48abe 100644
--- a/chrome/common/extensions/extension.cc
+++ b/chrome/common/extensions/extension.cc
@@ -1456,6 +1456,18 @@ bool Extension::InitFromValue(const DictionaryValue& source, bool require_key,
     }
   }
 
+  if (source.HasKey(keys::kOmniboxKeyword)) {
+    if (!source.GetString(keys::kOmniboxKeyword, &omnibox_keyword_) ||
+        omnibox_keyword_.empty()) {
+      *error = errors::kInvalidOmniboxKeyword;
+      return false;
+    }
+    if (!HasApiPermission(Extension::kExperimentalPermission)) {
+      *error = errors::kOmniboxExperimental;
+      return false;
+    }
+  }
+
   if (!CheckAppsAreEnabled(manifest_value_.get(), error) ||
       !LoadWebContentEnabled(manifest_value_.get(), error) ||
       !LoadWebOrigin(manifest_value_.get(), error) ||