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

chrome/browser/autocomplete/autocomplete_edit.cc

 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/autocomplete/autocomplete_edit.h"
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/string_util.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/app/chrome_dll_resource.h"
 #include "chrome/browser/autocomplete/autocomplete_classifier.h"
 #include "chrome/browser/autocomplete/autocomplete_edit_view.h"
 #include "chrome/browser/autocomplete/autocomplete_popup_model.h"
 #include "chrome/browser/autocomplete/keyword_provider.h"
 #include "chrome/browser/command_updater.h"
+#include "chrome/browser/extensions/extension_omnibox_api.h"
 #include "chrome/browser/metrics/user_metrics.h"
 #include "chrome/browser/net/dns_global.h"
 #include "chrome/browser/net/url_fixer_upper.h"
 #include "chrome/browser/profile.h"
 #include "chrome/browser/search_engines/template_url.h"
 #include "chrome/browser/search_engines/template_url_model.h"
 #include "chrome/common/notification_service.h"
 #include "chrome/common/url_constants.h"
 #include "googleurl/src/gurl.h"
 #include "googleurl/src/url_util.h"
@@ skipping 230 matching lines @@
       paste_and_go_alternate_nav_url_, AutocompletePopupModel::kNoMatch,
       std::wstring());
 }
 
 void AutocompleteEditModel::AcceptInput(WindowOpenDisposition disposition,
                                         bool for_drop) {
   // Get the URL and transition type for the selected entry.
   AutocompleteMatch match;
   GURL alternate_nav_url;
   GetInfoForCurrentText(&match, &alternate_nav_url);
+
+  if (match.template_url && match.template_url->IsExtensionKeyword()) {
+    // Strip the keyword + leading space off the input.
+    size_t prefix_length = match.template_url->keyword().size() + 1;
+    ExtensionOmniboxEventRouter::OnInputEntered(
+        profile_, match.template_url->GetExtensionId(),
+        WideToUTF8(match.fill_into_edit.substr(prefix_length)));
+    view_->RevertAll();
+    return;
+  }
+
   if (!match.destination_url.is_valid())
     return;
 
   if (UTF8ToWide(match.destination_url.spec()) == permanent_text_) {
     // When the user hit enter on the existing permanent URL, treat it like a
     // reload for scoring purposes.  We could detect this by just checking
     // user_input_in_progress_, but it seems better to treat "edits" that end
     // up leaving the URL unchanged (e.g. deleting the last character and then
     // retyping it) as reloads too.
     match.transition = PageTransition::RELOAD;
@@ skipping 321 matching lines @@
   bool is_keyword_hint = false;
   const AutocompleteResult* result =
       Details<const AutocompleteResult>(details).ptr();
   const AutocompleteResult::const_iterator match(result->default_match());
   if (match != result->end()) {
     if ((match->inline_autocomplete_offset != std::wstring::npos) &&
         (match->inline_autocomplete_offset < match->fill_into_edit.length())) {
       inline_autocomplete_text =
           match->fill_into_edit.substr(match->inline_autocomplete_offset);
     }
-    // Warm up DNS Prefetch Cache.
-    chrome_browser_net::DnsPrefetchUrl(match->destination_url,
-                                       IsPreconnectable(match->type));
+
+    if (!match->destination_url.SchemeIs(chrome::kExtensionScheme)) {
+      // Warm up DNS Prefetch Cache.
+      chrome_browser_net::DnsPrefetchUrl(match->destination_url,
+                                         IsPreconnectable(match->type));
+    }
+
     // We could prefetch the alternate nav URL, if any, but because there
     // can be many of these as a user types an initial series of characters,
     // the OS DNS cache could suffer eviction problems for minimal gain.
 
     is_keyword_hint = popup_->GetKeywordForMatch(*match, &keyword);
   }
 
   OnPopupDataChanged(inline_autocomplete_text, NULL, keyword, is_keyword_hint);
 }
 
@@ skipping 21 matching lines @@
     AutocompleteMatch* match,
     GURL* alternate_nav_url) const {
   if (popup_->IsOpen() || query_in_progress()) {
     popup_->InfoForCurrentSelection(match, alternate_nav_url);
   } else {
     profile_->GetAutocompleteClassifier()->Classify(
         UserTextFromDisplayText(view_->GetText()), GetDesiredTLD(), match,
         alternate_nav_url);
   }
 }