Disable the image notification property on MacOS

third_party/WebKit/Source/platform/RuntimeEnabledFeatures.json5

 {
   // http://dev.chromium.org/blink/runtime-enabled-features
   //
   // This list is used to generate RuntimeEnabledFeatures.h/cpp which contains
   // a class that stores static enablers for all experimental features.
 
   parameters: {
     // Each feature can be assigned a "status":
     // status=stable -> Enable this in all Blink configurations.  We are committed to these APIs indefinitely.
     // status=experimental -> In-progress features, Web Developers might play with, but are not on by default in stable.
@@ skipping 633 matching lines @@
       status: "stable",
     },
     {
       name: "NotificationBadge",
       status: "stable",
     },
     {
       name: "NotificationConstructor",
       status: "stable",
     },
+    // NotificationContentImage is not available in all platforms
     {
       name: "NotificationContentImage",
-      status: "stable",
+      status: "test",

[foolip, 2017/04/13 08:38:12]

Can you keep status "stable" and disable it on Mac instead? When trying to
figure out which parts of our IDL we are actually shipping, i.e. where it's
important that it matches the spec, it's a problem if it looks like a feature
isn't shipping but actually is. There are some cases, but the fewer the better.

     },
     {
       name: "NotificationInlineReplies",
       status: "experimental",
     },
     {
       name: "Notifications",
       status: "stable",
     },
     {
@@ skipping 372 matching lines @@
     {
       name: "Worklet",
       status: "experimental",
     },
     {
       name: "XSLT",
       status: "stable",
     },
   ],
 }