Add UserInputTracker, which keeps track of recent user input events.

chrome/browser/page_load_metrics/user_input_tracker_unittest.cc

Index: chrome/browser/page_load_metrics/user_input_tracker_unittest.cc
diff --git a/chrome/browser/page_load_metrics/user_input_tracker_unittest.cc b/chrome/browser/page_load_metrics/user_input_tracker_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..5ff1be79f04cf2360808c4f1b07cf6eda003b112
--- /dev/null
+++ b/chrome/browser/page_load_metrics/user_input_tracker_unittest.cc
@@ -0,0 +1,212 @@
+// Copyright (c) 2015 The Chromium Authors. All rights reserved.

[Charlie Harrison, 2016/12/05 19:17:46]

Copyright 2016

no (c)

[Bryan McQuade, 2016/12/06 01:52:25]

Ah, sure. I fixed a couple other tests in the same directory that had the same
pattern. Not really sure where we got that from. Perhaps it was the old
copyright statement.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/page_load_metrics/user_input_tracker.h"
+
+#include "base/time/time.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "third_party/WebKit/public/platform/WebInputEvent.h"
+

[Charlie Harrison, 2016/12/05 19:17:46]

Shouldn't these tests be in namespace page_load_metrics?

[Bryan McQuade, 2016/12/06 01:52:25]

I don't think so. Most of our tests don't follow this pattern (in the observers
directory).

[Charlie Harrison, 2016/12/06 18:43:09]

That was because originally the namespace was confined to the separate
component, and there were concerns with sharing the namespace across both
//components and //chrome. I think now that all code is in //chrome we can use
the namespace in tests. Most other namespaces like content and net do this.

[Bryan McQuade, 2016/12/06 20:10:03]

Ah, ok, I went ahead and made this change. I took a look at how often this
pattern is used in chrome/. There doesn't appear to be a convention one way or
the other:

git grep -l -E '^namespace [^{]' chrome/ | grep test.cc | wc -l
1008

git grep -L -E '^namespace [^{]' chrome/ | grep test.cc | wc -l
1062

So if my grep is correct, it's roughly 50/50, meaning no real convention in
chrome/. It would be nice if there was a convention across the codebase, but it
appears to vary a good bit.

+namespace {
+
+// UserInputTracker allows events to be at most 2 seconds old. Thus we use
+// 2100ms to make sure the age is greater than 2 seconds.
+const int kTooOldMilliseconds = 2100;
+
+double ToMonotonicallyIncreasingSeconds(base::TimeTicks t) {
+  return t.ToInternalValue() /

[Charlie Harrison, 2016/12/05 19:17:46]

Use (t - base::TimeTicks()).InSecondsF()

[Bryan McQuade, 2016/12/06 01:52:25]

Ah, nice, much better, thanks!

+         static_cast<double>(base::Time::kMicrosecondsPerSecond);
+}
+
+class FakeInputEvent : public blink::WebInputEvent {
+ public:
+  FakeInputEvent() : WebInputEvent(sizeof(FakeInputEvent)) {
+    timeStampSeconds = ToMonotonicallyIncreasingSeconds(base::TimeTicks::Now());
+    type = blink::WebInputEvent::Char;

[Charlie Harrison, 2016/12/05 19:17:47]

Should we vary on this to ensure we aren't recording mouse moves, e.g.?

[Bryan McQuade, 2016/12/06 01:52:25]

Added a test.

+  }
+
+  base::TimeTicks GetTimeStamp() {
+    return page_load_metrics::UserInputTracker::GetEventTime(*this);
+  }
+
+  base::TimeTicks GetTimeStampRounded() {
+    return page_load_metrics::UserInputTracker::RoundToRateLimitedOffset(
+        GetTimeStamp());
+  }
+};
+
+}  // namespace
+
+class UserInputTrackerTest : public testing::Test {};
+
+TEST_F(UserInputTrackerTest, Basic) {
+  page_load_metrics::UserInputTracker tracker;
+  EXPECT_EQ(base::TimeTicks(),
+            tracker.FindMostRecentUserInputEventBefore(base::TimeTicks()));
+  EXPECT_EQ(base::TimeTicks(),
+            tracker.FindMostRecentUserInputEventBefore(base::TimeTicks::Now()));
+}
+
+TEST_F(UserInputTrackerTest, SingleEvent) {
+  page_load_metrics::UserInputTracker tracker;
+  FakeInputEvent e;
+  tracker.OnInputEvent(e);
+
+  EXPECT_EQ(base::TimeTicks(), tracker.FindMostRecentUserInputEventBefore(
+                                   e.GetTimeStampRounded()));
+
+  base::TimeTicks after =
+      e.GetTimeStampRounded() + base::TimeDelta::FromMicroseconds(1);
+
+  EXPECT_EQ(e.GetTimeStampRounded(),
+            tracker.FindMostRecentUserInputEventBefore(after));
+
+  EXPECT_TRUE(tracker.FindAndConsumeInputEventsBefore(e.GetTimeStamp()));
+
+  EXPECT_EQ(base::TimeTicks(),
+            tracker.FindMostRecentUserInputEventBefore(after));
+}
+
+TEST_F(UserInputTrackerTest, MultipleEvents) {
+  FakeInputEvent e1;
+  FakeInputEvent e2;
+
+  // Make sure that the two events are monotonically increasing, and that both
+  // are in the past.
+  e1.timeStampSeconds = ToMonotonicallyIncreasingSeconds(
+      e2.GetTimeStamp() - base::TimeDelta::FromMilliseconds(100));
+
+  base::TimeTicks after =
+      e2.GetTimeStampRounded() + base::TimeDelta::FromMicroseconds(1);
+
+  {
+    page_load_metrics::UserInputTracker tracker;
+    tracker.OnInputEvent(e1);
+    tracker.OnInputEvent(e2);
+
+    EXPECT_EQ(base::TimeTicks(), tracker.FindMostRecentUserInputEventBefore(
+                                     e1.GetTimeStampRounded()));
+    EXPECT_EQ(
+        e1.GetTimeStampRounded(),
+        tracker.FindMostRecentUserInputEventBefore(e2.GetTimeStampRounded()));
+
+    EXPECT_EQ(e2.GetTimeStampRounded(),
+              tracker.FindMostRecentUserInputEventBefore(after));
+
+    EXPECT_TRUE(tracker.FindAndConsumeInputEventsBefore(e1.GetTimeStamp()));

[Charlie Harrison, 2016/12/05 19:17:46]

Why is this always true? Shouldn't e1 == event_times_.begin()? Could this flake
if rounding ends up being a no-op?

[Bryan McQuade, 2016/12/06 01:52:25]

Wow, this is just a straight up test bug, thanks for your attention to detail
here.

+    EXPECT_EQ(base::TimeTicks(), tracker.FindMostRecentUserInputEventBefore(
+                                     e1.GetTimeStampRounded()));
+    EXPECT_EQ(base::TimeTicks(), tracker.FindMostRecentUserInputEventBefore(
+                                     e2.GetTimeStampRounded()));
+    EXPECT_EQ(e2.GetTimeStampRounded(),
+              tracker.FindMostRecentUserInputEventBefore(after));
+
+    EXPECT_TRUE(tracker.FindAndConsumeInputEventsBefore(e2.GetTimeStamp()));
+    EXPECT_EQ(base::TimeTicks(), tracker.FindMostRecentUserInputEventBefore(
+                                     e1.GetTimeStampRounded()));
+    EXPECT_EQ(base::TimeTicks(), tracker.FindMostRecentUserInputEventBefore(
+                                     e2.GetTimeStampRounded()));
+    EXPECT_EQ(base::TimeTicks(),
+              tracker.FindMostRecentUserInputEventBefore(after));
+  }
+
+  {
+    page_load_metrics::UserInputTracker tracker;
+    tracker.OnInputEvent(e1);
+    tracker.OnInputEvent(e2);
+    EXPECT_EQ(e2.GetTimeStampRounded(),
+              tracker.FindMostRecentUserInputEventBefore(after));
+    EXPECT_TRUE(tracker.FindAndConsumeInputEventsBefore(e2.GetTimeStamp()));
+    EXPECT_EQ(base::TimeTicks(),
+              tracker.FindMostRecentUserInputEventBefore(after));
+  }
+}
+
+TEST_F(UserInputTrackerTest, IgnoreEventsOlderThanConsumed) {
+  FakeInputEvent e1;
+  FakeInputEvent e2;
+
+  // Make sure that the two events are monotonically increasing, and that both
+  // are in the past.
+  e1.timeStampSeconds = ToMonotonicallyIncreasingSeconds(
+      e2.GetTimeStamp() - base::TimeDelta::FromMilliseconds(100));
+
+  base::TimeTicks after =
+      e2.GetTimeStampRounded() + base::TimeDelta::FromMicroseconds(1);
+
+  page_load_metrics::UserInputTracker tracker;
+  tracker.OnInputEvent(e2);
+
+  EXPECT_EQ(base::TimeTicks(), tracker.FindMostRecentUserInputEventBefore(
+                                   e1.GetTimeStampRounded()));
+  EXPECT_EQ(base::TimeTicks(), tracker.FindMostRecentUserInputEventBefore(
+                                   e2.GetTimeStampRounded()));
+  EXPECT_EQ(e2.GetTimeStampRounded(),
+            tracker.FindMostRecentUserInputEventBefore(after));
+
+  EXPECT_TRUE(tracker.FindAndConsumeInputEventsBefore(e2.GetTimeStamp()));
+  EXPECT_EQ(base::TimeTicks(),
+            tracker.FindMostRecentUserInputEventBefore(after));
+
+  tracker.OnInputEvent(e1);
+  EXPECT_EQ(base::TimeTicks(), tracker.FindMostRecentUserInputEventBefore(
+                                   e1.GetTimeStampRounded()));
+  EXPECT_EQ(base::TimeTicks(), tracker.FindMostRecentUserInputEventBefore(
+                                   e1.GetTimeStampRounded() +
+                                   base::TimeDelta::FromMicroseconds(1)));
+}
+
+TEST_F(UserInputTrackerTest, ExcludeOldEvents) {
+  page_load_metrics::UserInputTracker tracker;
+  FakeInputEvent e1;
+  FakeInputEvent e2;
+  // make sure e1 is too old to be considered.
+  e1.timeStampSeconds = ToMonotonicallyIncreasingSeconds(
+      e2.GetTimeStamp() -
+      base::TimeDelta::FromMilliseconds(kTooOldMilliseconds));
+
+  tracker.OnInputEvent(e1);
+  tracker.OnInputEvent(e2);
+
+  EXPECT_EQ(base::TimeTicks(), tracker.FindMostRecentUserInputEventBefore(
+                                   e1.GetTimeStampRounded() +
+                                   base::TimeDelta::FromMilliseconds(1)));
+  EXPECT_EQ(base::TimeTicks(),
+            tracker.FindMostRecentUserInputEventBefore(
+                e2.GetTimeStampRounded() +
+                base::TimeDelta::FromMilliseconds(kTooOldMilliseconds)));
+  EXPECT_EQ(
+      e2.GetTimeStampRounded(),
+      tracker.FindMostRecentUserInputEventBefore(
+          e2.GetTimeStampRounded() + base::TimeDelta::FromMilliseconds(1)));

[Charlie Harrison, 2016/12/05 19:17:47]

Add test:
EXPECT_EQ(base::TimeTicks(),
tracker.FidnMostRecentUserInputEventBefore(e2.GetTimeStampRounded()) ?

[Bryan McQuade, 2016/12/06 01:52:25]

Done

+}
+
+TEST_F(UserInputTrackerTest, RateLimit) {
+  const size_t kTooManyEntries =
+      page_load_metrics::UserInputTracker::kMaxEntries * 5;
+
+  page_load_metrics::UserInputTracker tracker;
+  FakeInputEvent e;
+
+  // UserInputTracker DCHECKs that event timestamps aren't after the current
+  // time, so to be safe, we use a starting timestamp that is twice
+  // kTooManyEntries milliseconds in the past, and then synthesize one event for
+  // each of kTooManyEntries after this start point. This guarantees that all
+  // events are in the past.
+  e.timeStampSeconds = ToMonotonicallyIncreasingSeconds(
+      e.GetTimeStamp() -
+      base::TimeDelta::FromMilliseconds(kTooManyEntries * 2));
+
+  // Insert more than kMaxEntries entries. The rate limiting logic should
+  // prevent more than kMaxEntries entries from actually being inserted. A
+  // DCHECK in OnInputEvent verifies that we don't exceed the expected capacity.
+  for (size_t i = 0; i < kTooManyEntries; ++i) {
+    tracker.OnInputEvent(e);
+    e.timeStampSeconds += base::TimeDelta::FromMilliseconds(1).InSecondsF();
+  }
+
+  // Do a basic sanity check to make sure we can find events in the tracker.
+  EXPECT_NE(base::TimeTicks(),
+            tracker.FindMostRecentUserInputEventBefore(base::TimeTicks::Now()));
+}