[Mac] Maximise timer slack for background tabs

chrome/common/render_messages.h

 // Copyright (c) 2012 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.
 
 // Multiply-included file, no traditional include guard.
 #include <stdint.h>
 #include <map>
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 216 matching lines @@
 // Tells the renderer to set its maximum cache size to the supplied value.
 IPC_MESSAGE_CONTROL3(ChromeViewMsg_SetCacheCapacities,
                      size_t /* min_dead_capacity */,
                      size_t /* max_dead_capacity */,
                      size_t /* capacity */)
 
 // Tells the renderer to clear the cache.
 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.
 IPC_MESSAGE_ROUTED1(ChromeViewMsg_WebUIJavaScript,
                     base::string16  /* javascript */)
 
 // Set the content setting rules stored by the renderer.
 IPC_MESSAGE_CONTROL1(ChromeViewMsg_SetContentSettingRules,
                      RendererContentSettingRules /* rules */)
 
@@ skipping 463 matching lines @@
 // WebKit.
 IPC_MESSAGE_ROUTED4(ChromeViewHostMsg_DetailedConsoleMessageAdded,
                     base::string16 /* message */,
                     base::string16 /* source */,
                     extensions::StackTrace /* stack trace */,
                     int32 /* severity level */)
 
 // Sent by the renderer to check if crash reporting is enabled.
 IPC_SYNC_MESSAGE_CONTROL0_1(ChromeViewHostMsg_IsCrashReportingEnabled,
                             bool /* enabled */)