Revert CL 117933003. Re-add resource speculative prefetching code.

chrome/browser/net/resource_prefetch_predictor_observer.cc

Index: chrome/browser/net/resource_prefetch_predictor_observer.cc
diff --git a/chrome/browser/net/resource_prefetch_predictor_observer.cc b/chrome/browser/net/resource_prefetch_predictor_observer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..3a016fe7038e377528f2adfa66e46c950a467704
--- /dev/null
+++ b/chrome/browser/net/resource_prefetch_predictor_observer.cc
@@ -0,0 +1,202 @@
+// Copyright (c) 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.
+
+#include "chrome/browser/net/resource_prefetch_predictor_observer.h"
+
+#include <string>
+
+#include "base/metrics/histogram.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/public/browser/render_frame_host.h"
+#include "content/public/browser/resource_request_info.h"
+#include "net/url_request/url_request.h"
+#include "url/gurl.h"
+
+using content::BrowserThread;
+using predictors::ResourcePrefetchPredictor;
+
+namespace {
+
+// Enum for measuring statistics pertaining to observed request, responses and
+// redirects.
+enum RequestStats {
+  REQUEST_STATS_TOTAL_RESPONSES = 0,
+  REQUEST_STATS_TOTAL_PROCESSED_RESPONSES = 1,
+  REQUEST_STATS_NO_RESOURCE_REQUEST_INFO = 2,
+  REQUEST_STATS_NO_RENDER_FRAME_ID_FROM_REQUEST_INFO = 3,
+  REQUEST_STATS_MAX = 4,
+};
+
+// Specific to main frame requests.
+enum MainFrameRequestStats {
+  MAIN_FRAME_REQUEST_STATS_TOTAL_REQUESTS = 0,
+  MAIN_FRAME_REQUEST_STATS_PROCESSED_REQUESTS = 1,
+  MAIN_FRAME_REQUEST_STATS_TOTAL_REDIRECTS = 2,
+  MAIN_FRAME_REQUEST_STATS_PROCESSED_REDIRECTS = 3,
+  MAIN_FRAME_REQUEST_STATS_TOTAL_RESPONSES = 4,
+  MAIN_FRAME_REQUEST_STATS_PROCESSED_RESPONSES = 5,
+  MAIN_FRAME_REQUEST_STATS_MAX = 6,
+};
+
+void ReportRequestStats(RequestStats stat) {
+  UMA_HISTOGRAM_ENUMERATION("ResourcePrefetchPredictor.RequestStats",

[Lei Zhang, 2014/09/09 03:32:19]

You need to update the histograms xml file and have a metrics OWNER review this.

[Zhen Wang, 2014/09/13 00:36:31]

The main purpose of this CL is to bring back the old code, resolve all the
conflicts and make it work with current browser architecture. The feature is
disabled for now and will not affect current browser usage and experiment. We
have plans to examine all the metrics in the original code, write up the formal
finch experiment description and enable the experiment in later CLs.

See also:
https://code.google.com/p/chromium/issues/detail?id=405690#c12
https://code.google.com/p/chromium/issues/detail?id=406200
https://code.google.com/p/chromium/issues/detail?id=406203

+                            stat,
+                            REQUEST_STATS_MAX);
+}
+
+void ReportMainFrameRequestStats(MainFrameRequestStats stat) {
+  UMA_HISTOGRAM_ENUMERATION("ResourcePrefetchPredictor.MainFrameRequestStats",
+                            stat,
+                            MAIN_FRAME_REQUEST_STATS_MAX);
+}
+
+bool SummarizeResponse(net::URLRequest* request,
+                       ResourcePrefetchPredictor::URLRequestSummary* summary) {
+  const content::ResourceRequestInfo* info =
+      content::ResourceRequestInfo::ForRequest(request);
+  if (!info) {
+    ReportRequestStats(REQUEST_STATS_NO_RESOURCE_REQUEST_INFO);
+    return false;
+  }
+
+  int render_process_id, render_frame_id;
+  if (!info->GetAssociatedRenderFrame(&render_process_id, &render_frame_id)) {
+    ReportRequestStats(REQUEST_STATS_NO_RENDER_FRAME_ID_FROM_REQUEST_INFO);
+    return false;
+  }
+
+  summary->navigation_id.render_process_id = render_process_id;
+  summary->navigation_id.render_frame_id = render_frame_id;
+  summary->navigation_id.main_frame_url = request->first_party_for_cookies();
+  summary->navigation_id.creation_time = request->creation_time();
+  summary->resource_url = request->original_url();
+  summary->resource_type = info->GetResourceType();
+  request->GetMimeType(&summary->mime_type);
+  summary->was_cached = request->was_cached();
+
+  // Use the mime_type to determine the resource type for subresources since
+  // types such as PREFETCH, SUB_RESOURCE, etc are not useful.
+  if (summary->resource_type != content::RESOURCE_TYPE_MAIN_FRAME) {
+    summary->resource_type =
+        ResourcePrefetchPredictor::GetResourceTypeFromMimeType(
+            summary->mime_type,
+            summary->resource_type);
+  }
+  return true;
+}
+
+}  // namespace
+
+namespace chrome_browser_net {
+
+ResourcePrefetchPredictorObserver::ResourcePrefetchPredictorObserver(
+    ResourcePrefetchPredictor* predictor)
+    : predictor_(predictor->AsWeakPtr()) {
+  CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+}
+
+ResourcePrefetchPredictorObserver::~ResourcePrefetchPredictorObserver() {
+  CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI) ||
+        BrowserThread::CurrentlyOn(BrowserThread::IO));
+}
+
+void ResourcePrefetchPredictorObserver::OnRequestStarted(
+    net::URLRequest* request,
+    content::ResourceType resource_type,
+    int child_id,
+    int frame_id) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));

[Lei Zhang, 2014/09/09 03:32:19]

nit: Please try to use DCHECK_CURRENTLY_ON() in new code.

[Zhen Wang, 2014/09/13 00:36:31]

Done.

+
+  if (resource_type == content::RESOURCE_TYPE_MAIN_FRAME)
+    ReportMainFrameRequestStats(MAIN_FRAME_REQUEST_STATS_TOTAL_REQUESTS);
+
+  if (!ResourcePrefetchPredictor::ShouldRecordRequest(request, resource_type))
+    return;
+
+  ResourcePrefetchPredictor::URLRequestSummary summary;
+  summary.navigation_id.render_process_id = child_id;
+  summary.navigation_id.render_frame_id = frame_id;
+  summary.navigation_id.main_frame_url = request->first_party_for_cookies();
+  summary.resource_url = request->original_url();
+  summary.resource_type = resource_type;
+
+  BrowserThread::PostTask(
+      BrowserThread::UI,
+      FROM_HERE,
+      base::Bind(&ResourcePrefetchPredictor::RecordURLRequest,
+                 predictor_,
+                 summary));
+
+  if (resource_type == content::RESOURCE_TYPE_MAIN_FRAME)
+    ReportMainFrameRequestStats(MAIN_FRAME_REQUEST_STATS_PROCESSED_REQUESTS);
+}
+
+void ResourcePrefetchPredictorObserver::OnRequestRedirected(
+    const GURL& redirect_url,
+    net::URLRequest* request) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+
+  const content::ResourceRequestInfo* request_info =
+      content::ResourceRequestInfo::ForRequest(request);
+  if (request_info &&
+      request_info->GetResourceType() == content::RESOURCE_TYPE_MAIN_FRAME) {
+    ReportMainFrameRequestStats(MAIN_FRAME_REQUEST_STATS_TOTAL_REDIRECTS);
+  }
+
+  if (!ResourcePrefetchPredictor::ShouldRecordRedirect(request))
+    return;
+
+  ResourcePrefetchPredictor::URLRequestSummary summary;
+  if (!SummarizeResponse(request, &summary))
+    return;
+
+  summary.redirect_url = redirect_url;
+
+  BrowserThread::PostTask(
+      BrowserThread::UI,
+      FROM_HERE,
+      base::Bind(&ResourcePrefetchPredictor::RecordURLRedirect,
+                 predictor_,
+                 summary));
+
+  if (request_info &&
+      request_info->GetResourceType() == content::RESOURCE_TYPE_MAIN_FRAME) {
+    ReportMainFrameRequestStats(MAIN_FRAME_REQUEST_STATS_PROCESSED_REDIRECTS);
+  }
+}
+
+void ResourcePrefetchPredictorObserver::OnResponseStarted(
+    net::URLRequest* request) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+
+  ReportRequestStats(REQUEST_STATS_TOTAL_RESPONSES);
+
+  const content::ResourceRequestInfo* request_info =
+      content::ResourceRequestInfo::ForRequest(request);
+  if (request_info &&
+      request_info->GetResourceType() == content::RESOURCE_TYPE_MAIN_FRAME) {
+    ReportMainFrameRequestStats(MAIN_FRAME_REQUEST_STATS_TOTAL_RESPONSES);
+  }
+
+  if (!ResourcePrefetchPredictor::ShouldRecordResponse(request))
+    return;
+  ResourcePrefetchPredictor::URLRequestSummary summary;
+  if (!SummarizeResponse(request, &summary))
+    return;
+
+  BrowserThread::PostTask(
+      BrowserThread::UI,
+      FROM_HERE,
+      base::Bind(&ResourcePrefetchPredictor::RecordURLResponse,
+                 predictor_,
+                 summary));
+
+  ReportRequestStats(REQUEST_STATS_TOTAL_PROCESSED_RESPONSES);
+  if (request_info &&
+      request_info->GetResourceType() == content::RESOURCE_TYPE_MAIN_FRAME) {
+    ReportMainFrameRequestStats(MAIN_FRAME_REQUEST_STATS_PROCESSED_RESPONSES);
+  }
+}
+
+}  // namespace chrome_browser_net