Enable Purge+throttle by default except Android and MacOS.

content/public/common/content_features.cc

Index: content/public/common/content_features.cc
diff --git a/content/public/common/content_features.cc b/content/public/common/content_features.cc
index 3c53154fbb617fadd462716e2253118d358fbed4..debefe332832f97e5276f7b1cb40e56541f171f9 100644
--- a/content/public/common/content_features.cc
+++ b/content/public/common/content_features.cc
@@ -151,8 +151,14 @@ const base::Feature kPointerEvents{"PointerEvent",
                                    base::FEATURE_ENABLED_BY_DEFAULT};
 
 // Enables purge and suspend.
-const base::Feature kPurgeAndSuspend{"PurgeAndSuspend",
-                                     base::FEATURE_DISABLED_BY_DEFAULT};
+const base::Feature kPurgeAndSuspend {
+  "PurgeAndSuspend",
+#if defined(OS_MACOSX) || defined(OS_ANDROID)

[Wez, 2017/03/29 23:50:55]

Is there a bug with context on why we don't enable this for Mac OS, that you
could add a comment to link to here?

[tasak, 2017/03/30 09:26:12]

Added.
So this comment looks ok?

+      base::FEATURE_DISABLED_BY_DEFAULT
+#else
+      base::FEATURE_ENABLED_BY_DEFAULT
+#endif
+};
 
 // RAF aligned mouse input events support.
 const base::Feature kRafAlignedMouseInputEvents{