Move ranker_model_loader to a new component.

components/machine_intelligence/ranker_url_fetcher.cc

Index: components/machine_intelligence/ranker_url_fetcher.cc
diff --git a/components/machine_intelligence/ranker_url_fetcher.cc b/components/machine_intelligence/ranker_url_fetcher.cc
new file mode 100644
index 0000000000000000000000000000000000000000..965d716d76b1e1b55389b82b0f9a317e4193f940
--- /dev/null
+++ b/components/machine_intelligence/ranker_url_fetcher.cc
@@ -0,0 +1,109 @@
+// Copyright 2017 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 "components/machine_intelligence/ranker_url_fetcher.h"
+
+#include "base/memory/ref_counted.h"
+#include "components/data_use_measurement/core/data_use_user_data.h"
+#include "net/base/load_flags.h"
+#include "net/http/http_status_code.h"
+#include "net/traffic_annotation/network_traffic_annotation.h"
+#include "net/url_request/url_fetcher.h"
+#include "net/url_request/url_request_status.h"
+
+namespace machine_intelligence {
+
+namespace {
+
+// Retry parameter for fetching.
+const int kMaxRetry = 16;
+
+}  // namespace
+
+RankerURLFetcher::RankerURLFetcher() : state_(IDLE), retry_count_(0) {}
+
+RankerURLFetcher::~RankerURLFetcher() {}
+
+bool RankerURLFetcher::Request(
+    const GURL& url,
+    const RankerURLFetcher::Callback& callback,
+    net::URLRequestContextGetter* request_context_getter) {
+  // This function is not supposed to be called if the previous operation is not
+  // finished.
+  if (state_ == REQUESTING) {
+    NOTREACHED();
+    return false;
+  }
+
+  if (retry_count_ >= kMaxRetry)
+    return false;
+  retry_count_++;
+
+  state_ = REQUESTING;
+  url_ = url;
+  callback_ = callback;
+
+  if (request_context_getter == nullptr)
+    return false;
+
+  net::NetworkTrafficAnnotationTag traffic_annotation =
+      net::DefineNetworkTrafficAnnotation("ranker_url_fetcher", R"(
+        semantics {
+          sender: "AssistRanker"
+          description:
+            "Chrome can provide a better UI experience by using machine "
+            "learning models to determine if we should show you or not an "
+            "assist prompt. For instance, Chrome may use features such as "
+            "the detected language of the current page and the past "
+            "interaction with the TransalteUI to decide whether or not we "
+            "should offer you to translate this page. Google returns "
+            "trained machine learning models that will be used to take "
+            "such decision."
+          trigger:
+            "At startup."
+          data:
+            "Path to a model. No user data is included."
+          destination: GOOGLE_OWNED_SERVICE
+        }
+        policy {
+          cookies_allowed: false
+          setting:
+            "NA"
+        })");
+  // Create and initialize the URL fetcher.
+  fetcher_ = net::URLFetcher::Create(url_, net::URLFetcher::GET, this,
+                                     traffic_annotation);
+  data_use_measurement::DataUseUserData::AttachToFetcher(
+      fetcher_.get(),
+      data_use_measurement::DataUseUserData::MACHINE_INTELLIGENCE);
+  fetcher_->SetLoadFlags(net::LOAD_DO_NOT_SEND_COOKIES |
+                         net::LOAD_DO_NOT_SAVE_COOKIES);
+  fetcher_->SetRequestContext(request_context_getter);
+
+  // Set retry parameter for HTTP status code 5xx. This doesn't work against
+  // 106 (net::ERR_INTERNET_DISCONNECTED) and so on.
+  fetcher_->SetMaxRetriesOn5xx(max_retry_on_5xx_);
+  fetcher_->Start();
+
+  return true;
+}
+
+void RankerURLFetcher::OnURLFetchComplete(const net::URLFetcher* source) {
+  DCHECK(fetcher_.get() == source);
+
+  std::string data;
+  if (source->GetStatus().status() == net::URLRequestStatus::SUCCESS &&
+      source->GetResponseCode() == net::HTTP_OK) {
+    state_ = COMPLETED;
+    source->GetResponseAsString(&data);
+  } else {
+    state_ = FAILED;
+  }
+
+  // Transfer URLFetcher's ownership before invoking a callback.
+  std::unique_ptr<const net::URLFetcher> delete_ptr(fetcher_.release());
+  callback_.Run(state_ == COMPLETED, data);
+}
+
+}  // namespace machine_intelligence