[Mac] Maximise timer slack for background tabs

chrome/common/render_messages.h

Index: chrome/common/render_messages.h
diff --git a/chrome/common/render_messages.h b/chrome/common/render_messages.h
index d6cfa7c5b62c5a4a23f0ad56e2371e8b72b58acd..cce224415f28c8d60e7c9ef2030ac5621facce46 100644
--- a/chrome/common/render_messages.h
+++ b/chrome/common/render_messages.h
@@ -234,6 +234,10 @@ IPC_MESSAGE_CONTROL3(ChromeViewMsg_SetCacheCapacities,
 IPC_MESSAGE_CONTROL1(ChromeViewMsg_ClearCache,
                      bool /* on_navigation */)
 
+IPC_MESSAGE_CONTROL1(ChromeViewMsg_SetCoalesceTimers,
+                    bool /* enabled */)

[tonyg, 2014/05/20 14:14:52]

I might be missing something, but the renderer already knows whether it is
visible or audible. Then it notifies the browser which now turns around and
notifies the renderer to coalesce timers. I'm wondering now whether the logic to
apply coalescing should live in the renderer process to avoid the extra ipc.

Also, I think everywhere we talk about coalescing, we should pass a timer_slack
enum instead of a bool. That way if we add a small coalescing (in between NONE
and MAXIMUM), we don't have to rework the API. For instance, we may discover
with experimentation that even the foreground tab could handle 5 or 10% slack.

+
+
 // For WebUI testing, this message requests JavaScript to be executed at a time
 // which is late enough to not be thrown out, and early enough to be before
 // onload events are fired.