NTP: simplify mojo connection setup

chrome/common/instant.mojom

 // Copyright 2016 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.
 
 module chrome.mojom;
 
 import "mojo/common/string16.mojom";
 import "mojo/common/time.mojom";
 import "url/mojo/url.mojom";
 
 [Native]
 enum NTPLoggingEventType;
 
 [Native]
 enum OmniboxFocusState;
 
 [Native]
 enum NTPTileSource;
 
+// Interface used to connect to the embedded search interface. This is a
+// separate interface such that a reverse connection (|client| below) can be
+// passed when connecting.
+interface EmbeddedSearchConnector {
+  // Connect to the interface. |instant| is the connection which the client will
+  // use to query the embedded search interface. |client| is the connection used
+  // by the embedded search interface implementation to push browser state
+  // updates to the client.
+  Connect(associated Instant& instant, associated SearchBox client);
+};
+
+// TODO(tibell): Rename this to EmbeddedSearch.
+//
+// Browser interface to support embedded search. Render frames connect to this
+// interface to query browser data, such as the most visited pages.
 interface Instant {
   // Tells InstantExtended whether the embedded search API is supported.
   // See http://dev.chromium.org/embeddedsearch
   InstantSupportDetermined(int32 page_seq_no, bool result);
 
   // Tells InstantExtended to set the omnibox focus state.
   FocusOmnibox(int32 page_seq_no, OmniboxFocusState state);
 
   // TODO(treib): Remove the SearchBox prefix from these three methods.
   // Tells InstantExtended to delete a most visited item.
@@ skipping 41 matching lines @@
 
 [Native]
 struct InstantSuggestion;
 
 [Native]
 struct EmbeddedSearchRequestParams;
 
 [Native]
 struct ThemeBackgroundInfo;
 
+// TODO(tibell): Rename this to EmbeddedSearchClient.
+//
+// Renderer interface used by the browser to push updates to the client. For
+// example, the browser will tell the frame if the omnibox got focus.
 interface SearchBox {
   SetPageSequenceNumber(int32 page_seq_no);
 
   DetermineIfPageSupportsInstant();
 
   FocusChanged(OmniboxFocusState new_focus_state,
                OmniboxFocusChangeReason reason);
 
   MostVisitedChanged(array<InstantMostVisitedItem> items);
 
   SetInputInProgress(bool input_in_progress);
 
   SetSuggestionToPrefetch(InstantSuggestion suggestion);
 
   Submit(mojo.common.mojom.String16 value,
          EmbeddedSearchRequestParams params);
 
   ThemeChanged(ThemeBackgroundInfo value);
 
+  // TODO(treib): Remove the *Result methods and instead add return values to
+  // the correspnding methods in the Instant interface above.

[Marc Treib, 2017/02/09 09:30:47]

Ah, is this something made possible by Mojo? Nice!

[tibell, 2017/02/09 22:32:01]

Yup! It's convenient and also removes the need to use e.g. tokens in the
messages to associate requests with responses. The method implementor just gets
passed a base::Callback that is used to reply.

   HistorySyncCheckResult(bool sync_history);
 
   ChromeIdentityCheckResult(mojo.common.mojom.String16 identity,
                             bool identity_match);
 };