Chromium doesn't compile with -Wglobal-constructors

chrome/browser/page_load_metrics/user_input_tracker.cc

 // Copyright 2016 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/page_load_metrics/user_input_tracker.h"
 
 #include <algorithm>
 
 #include "third_party/WebKit/public/platform/WebInputEvent.h"
 
 namespace page_load_metrics {
 
 namespace {
 
 // Blink's UserGestureIndicator allows events to be associated with gestures
 // that are up to 1 second old, based on guidance in the HTML spec:
 // https://html.spec.whatwg.org/multipage/interaction.html#triggered-by-user-activation.
 const int kMaxEventAgeSeconds = 1;
 
 // Allow for up to 2x the oldest time. This allows consumers to continue to
 // find events for timestamps up to 1 second in the past.
 const int kOldestAllowedEventAgeSeconds = kMaxEventAgeSeconds * 2;
 
 // In order to limit to at most kMaxTrackedEvents, we rate limit the recorded
 // events,
 // allowing one per rate limit period.
-const int kRateLimitClampMillis = (kOldestAllowedEventAgeSeconds * 1000) /
-                                  UserInputTracker::kMaxTrackedEvents;
+constexpr int kRateLimitClampMillis = (kOldestAllowedEventAgeSeconds * 1000) /
+                                      UserInputTracker::kMaxTrackedEvents;
 
 bool IsInterestingInputEvent(const blink::WebInputEvent& event) {
   // Ignore synthesized auto repeat events.
   if (event.modifiers() & blink::WebInputEvent::IsAutoRepeat)
     return false;
 
   switch (event.type()) {
     case blink::WebInputEvent::MouseDown:
     case blink::WebInputEvent::MouseUp:
     case blink::WebInputEvent::RawKeyDown:
@@ skipping 17 matching lines @@
 }
 
 }  // namespace
 
 UserInputTracker::UserInputTracker() {
   sorted_event_times_.reserve(kMaxTrackedEvents);
 }
 
 UserInputTracker::~UserInputTracker() {}
 
-const size_t UserInputTracker::kMaxTrackedEvents = 100;
+constexpr size_t UserInputTracker::kMaxTrackedEvents;

[Charlie Harrison, 2017/01/30 14:17:51]

Can you move this bit of code nearer to the kRateLimitClampMillis definition? I
assume that's the only place we need this to be constexpr.

[ckulakowski, 2017/01/30 15:46:56]

Done.

 
 // static
 base::TimeTicks UserInputTracker::GetEventTime(
     const blink::WebInputEvent& event) {
   return GetTimeTicksFromSeconds(event.timeStampSeconds());
 }
 
 // static
 base::TimeTicks UserInputTracker::RoundToRateLimitedOffset(
     base::TimeTicks time) {
@@ skipping 95 matching lines @@
       std::upper_bound(sorted_event_times_.begin(), sorted_event_times_.end(),
                        cutoff));
 }
 
 // static
 base::TimeDelta UserInputTracker::GetOldEventThreshold() {
   return base::TimeDelta::FromSeconds(kOldestAllowedEventAgeSeconds);
 }
 
 }  // namespace page_load_metrics