[Mac] Maximise timer slack for background tabs

chrome/renderer/chrome_render_process_observer.cc

Index: chrome/renderer/chrome_render_process_observer.cc
diff --git a/chrome/renderer/chrome_render_process_observer.cc b/chrome/renderer/chrome_render_process_observer.cc
index 61c22ec2f19ac9a28ba068200332d015dde01abb..03d71367e3b97dd229508e4b09367498f3c505e7 100644
--- a/chrome/renderer/chrome_render_process_observer.cc
+++ b/chrome/renderer/chrome_render_process_observer.cc
@@ -13,6 +13,7 @@
 #include "base/file_util.h"
 #include "base/memory/weak_ptr.h"
 #include "base/message_loop/message_loop.h"
+#include "base/message_loop/timer_slack.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram.h"
 #include "base/metrics/statistics_recorder.h"
@@ -313,6 +314,8 @@ bool ChromeRenderProcessObserver::OnControlMessageReceived(
                         OnGetCacheResourceStats)
     IPC_MESSAGE_HANDLER(ChromeViewMsg_SetContentSettingRules,
                         OnSetContentSettingRules)
+     IPC_MESSAGE_HANDLER(ChromeViewMsg_SetCoalesceTimers,
+                         OnSetTimerCoalescing)
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
   return handled;
@@ -354,6 +357,13 @@ void ChromeRenderProcessObserver::OnSetContentSettingRules(
   content_setting_rules_ = rules;
 }
 
+void ChromeRenderProcessObserver::OnSetTimerCoalescing(bool enabled) {
+  base::TimerSlack timer_slack = base::TIMER_SLACK_NONE;
+  if (enabled)
+    timer_slack = base::TIMER_SLACK_MAXIMUM;
+  base::SetTimerSlack(timer_slack);
+}
+
 void ChromeRenderProcessObserver::OnSetCacheCapacities(size_t min_dead_capacity,
                                                        size_t max_dead_capacity,
                                                        size_t capacity) {