PageLoadMetrics renderer and browser implementation (deprecated)

components/page_load_metrics/renderer/page_load_metrics_render_frame_observer.cc

+// Copyright 2015 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 "base/time/time.h"
+#include "base/timer/timer.h"
+#include "components/page_load_metrics/renderer/page_load_metrics_render_frame_observer.h"
+#include "components/page_load_metrics/renderer/page_timing_metrics_sender.h"
+#include "content/public/renderer/render_frame.h"
+#include "third_party/WebKit/public/platform/WebURLResponse.h"
+#include "third_party/WebKit/public/web/WebDataSource.h"
+#include "third_party/WebKit/public/web/WebDocument.h"
+#include "third_party/WebKit/public/web/WebLocalFrame.h"
+#include "third_party/WebKit/public/web/WebPerformance.h"
+#include "url/gurl.h"
+
+namespace page_load_metrics {
+
+PageLoadMetricsRenderFrameObserver::PageLoadMetricsRenderFrameObserver(
+    content::RenderFrame* render_frame)
+    : content::RenderFrameObserver(render_frame) {}
+
+PageLoadMetricsRenderFrameObserver::~PageLoadMetricsRenderFrameObserver() {}
+
+// TODO(bmcquade): use DidChangePerformanceTiming instead, once available.
+void PageLoadMetricsRenderFrameObserver::DidFinishDocumentLoad() {
+  SendMetrics();
+}
+
+// TODO(bmcquade): use DidChangePerformanceTiming instead, once available.
+void PageLoadMetricsRenderFrameObserver::DidFinishLoad() {
+  SendMetrics();
+}
+
+void PageLoadMetricsRenderFrameObserver::DidStartProvisionalLoad() {
+  // A provisional page load has started. Shut down metrics reporting until the
+  // next page load is committed. Note that a provisoinal load may fail. We
+  // simply stop reporting metrics in that case, until the next successful page
+  // load is committed.
+  page_timing_metrics_sender_.reset();
+}
+
+void PageLoadMetricsRenderFrameObserver::DidCommitProvisionalLoad(
+    bool is_new_navigation, bool is_same_page_navigation) {
+  // Same-page navigations (e.g. an in-document navigation from a fragment
+  // link) aren't full page loads, since they don't go to network to load the
+  // main HTML resource. DidStartProvisionalLoad doesn't get invoked for same
+  // page navigations, so we may still have an active
+  // page_timing_metrics_sender_ at this point.
+  if (is_same_page_navigation)
+    return;
+
+  // TODO(bmcquade): what about data: and blob: URLs?
+  DCHECK(!page_timing_metrics_sender_);
+
+  // We only create a PageTimingMetricsSender if the page meets the criteria for
+  // sending and recording metrics. Once page_timing_metrics_sender_ is
+  // non-null, we will send metrics for the current page at some later time, as
+  // those metrics become available.

[nasko, 2015/08/26 17:27:24]

You won't get all the events in 1 second after the commit, especially on slower
loads and devices. Since you are using one shot timer, it is very likely a
non-trivial portion of the timing data will not contain full information.

[Bryan McQuade, 2015/08/26 18:28:00]

Though we use a OneShotTimer, the timer gets restarted each time new metrics are
received if the timer has already fired (from page_timing_metrics_sender.cc):

if (!timer_->IsRunning())
  timer_->Start(FROM_HERE,
      base::TimeDelta::FromMilliseconds(kTimerDelayMillis),
      base::Bind(&PageTimingMetricsSender::SendNow, base::Unretained(this)));

As best I can tell, OneShotTimer isn't one-shot in the sense that you start it
once, it fires once, and then you discard it, but rather in the sense that it is
non repeating, but can still be started multiple times. At least, that's my
understanding (I see other places in the codebase where it's used that way). If
you do think that's incorrect use, though, happy to figure out how to change it.

+  if (ShouldSendMetrics())
+    page_timing_metrics_sender_.reset(
+        new PageTimingMetricsSender(this, routing_id(), CreateTimer()));
+}
+
+void PageLoadMetricsRenderFrameObserver::SendMetrics() {
+  if (!page_timing_metrics_sender_)
+    return;
+
+  PageLoadTiming timing(GetTiming());
+  page_timing_metrics_sender_->Send(timing);
+}
+
+bool PageLoadMetricsRenderFrameObserver::ShouldSendMetrics() const {
+  const blink::WebLocalFrame& frame = *render_frame()->GetWebFrame();
+  // We only generate historgrams for main frames.
+  if (frame.parent())
+    return false;
+
+  const blink::WebDocument& document = frame.document();
+  // Ignore non-HTTP schemes (e.g. chrome://).
+  const GURL& url = document.url();
+  if (!url.SchemeIsHTTPOrHTTPS())
+    return false;
+
+  const blink::WebURLResponse& url_response = frame.dataSource()->response();
+  // Ignore multipart responses (e.g. MHTML).
+  if (url_response.isMultipartPayload())
+    return false;
+
+  // Ignore non-HTML documents (e.g. SVG). Note that images are treated by
+  // Blink as HTML documents, so to exclude images, we must perform
+  // additional mime type checking below.
+  if (!document.isHTMLDocument() && !document.isXHTMLDocument())
+    return false;
+
+  // Ignore non-HTML mime types (e.g. images).
+  std::string mime_type = url_response.mimeType().utf8();
+  if (mime_type != "text/html" && mime_type != "application/xhtml+xml")
+    return false;
+
+  return true;
+}
+
+PageLoadTiming PageLoadMetricsRenderFrameObserver::GetTiming() const {
+  PageLoadTiming timing;
+  blink::WebLocalFrame* frame = render_frame()->GetWebFrame();
+  if (frame) {
+    blink::WebPerformance performance = frame->performance();
+    timing.navigation_start =

[nasko, 2015/08/26 17:27:24]

Why not create a copy constructor for PageLoadTiming that takes
blink::WebPerformance as input? That way we have only one place that does type
transformation.

Alternatively, why do we even need PageLoadTiming? Can't we just reuse the
blink::WebPerformance?

[Bryan McQuade, 2015/08/26 18:28:00]

+1 to copy constructor that takes a WebPerformance. Will make that change.

I don't think we can use WebPerformance directly without nontrivial refactoring
in blink. As far as I can tell, there's no way to reconstruct a WebPerformance
object from raw data, which we'd need to do on the receiving end of this IPC in
the browser process. There are no setters on WebPerformance
(https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...)
and WebPerformanceImpl is backed by objects private to blink, rather than data
members, so adding setter support would be nontrivial. If there's something I'm
missing that does allow us to use WebPerformance directly though, let me know -
would definitely like to have fewer structs/classes if possible.

+        base::Time::FromDoubleT(performance.navigationStart());
+    timing.response_start =
+        base::Time::FromDoubleT(performance.responseStart());
+    timing.dom_content_loaded_event_start =
+        base::Time::FromDoubleT(performance.domContentLoadedEventStart());
+    timing.load_event_start =
+        base::Time::FromDoubleT(performance.loadEventStart());
+    timing.first_layout = base::Time::FromDoubleT(performance.firstLayout());
+  }
+  return timing;
+}
+
+scoped_ptr<base::Timer>
+PageLoadMetricsRenderFrameObserver::CreateTimer() const {
+  return scoped_ptr<base::Timer>(
+      new base::OneShotTimer<PageTimingMetricsSender>());
+}
+
+}  // namespace page_load_metrics