Bring up of the enhanced bookmarks cluster service.

components/enhanced_bookmarks/proto/cluster.proto

Index: components/enhanced_bookmarks/proto/cluster.proto
diff --git a/components/enhanced_bookmarks/proto/cluster.proto b/components/enhanced_bookmarks/proto/cluster.proto
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+// Copyright 2014 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.
+//
+syntax = "proto2";
+option optimize_for = LITE_RUNTIME;
+
+package image_collections;
+
+message ClusterRequest {
+  // Optional list of docs we want to cluster--a subset of the user's available
+  // docs.
+  repeated string docs = 1;
+
+  // When docs is empty, used to determine which clips are clustered.  If set to
+  // true, cluster all the user's clips.  Otherwise (default) cluster all of the
+  // user's uncategorized clips.
+  optional bool cluster_all = 3 [default = false];
+
+  optional HypnoOptions options = 2;
+}
+
+message ClusterResponse {
+  message Cluster {
+    repeated string docs = 1;
+    // May be empty or unset if no reasonable title could be found.
+    optional string title = 2;
+  }
+
+  // Each of ClusterRequest.docs will exist in exactly one cluster. Some
+  // clusters may be singletons, so
+  //   ClusterResponse.clusters_size() <= ClusterRequest.docs_size().
+  repeated Cluster clusters = 1;
+}
+
+// Options proto used for tuning and RPC requests.
+message HypnoOptions {
+  optional float min_merge_similarity = 1 [default = 0.14];
+  optional float min_linkage_similarity = 2 [default = 0.12];
+
+  // GAIA ID to use for requests received via RPC.
+  optional int64 gaia_id = 3 [default = 0];
+
+  // Options for limiting what is returned from cluster.
+  optional int32 min_cluster_size = 4 [default = 3];
+  optional bool include_unnamed_clusters = 5 [default = false];
+
+  // Options for webref usage.  Currently only honored in Superroot.
+  optional int32 min_webref_topicality = 6 [default = 30];
+  optional float webref_topicality_scaling = 7 [default = 1.0];
+}