Bug 1443252 - Make nsGlobalWindowInner/Outer final to reduce build times. r=mystor

In Bug 1332680 we got a list of classes and methods we could mark 'final',
as suggested by an LTO build of gcc. One of the items on that list was
nsGlobalWindowInner and nsGlobalWindowOuter, with quite a lot of virtual
calls:

> dom/base/nsGlobalWindowInner.h:206:7: warning: Declaring type 'struct nsGlobalWindowInner' final would enable devirtualization of 483 calls
> dom/base/nsGlobalWindowOuter.h:164:7: warning: Declaring type 'struct nsGlobalWindowOuter' final would enable devirtualization of 143 calls

After trying it out, we saw a modest improvement to a single Talos tes
(displaylist mutate got 4-8.5% better). That's not the interesting
thing though.

For Linux and OSX (and some flavors of Android) build times were reduced
by half across the board. They're a bit variable of course, but 30-70%
improvements are shown by Talos. Windows and other flavors of Android
show 10-15% improvements.

MozReview-Commit-ID: GlEGBt2JOTt

dom/base/nsGlobalWindowInner.h

@@ -204,18 +204,19 @@ ImplCycleCollectionTraverse(nsCycleCollectionTraversalCallback& aCallback,
 // inner windows belonging to the same outer window, but that's an unimportant
 // side effect of inheriting PRCList).
 
-class nsGlobalWindowInner : public mozilla::dom::EventTarget,
-                            public nsPIDOMWindowInner,
-                            private nsIDOMWindow,
-                            // NOTE: This interface is private, as it's only
-                            // implemented on chrome windows.
-                            private nsIDOMChromeWindow,
-                            public nsIScriptGlobalObject,
-                            public nsIScriptObjectPrincipal,
-                            public nsSupportsWeakReference,
-                            public nsIInterfaceRequestor,
-                            public PRCListStr,
-                            public nsAPostRefreshObserver
+class nsGlobalWindowInner final
+  : public mozilla::dom::EventTarget
+  , public nsPIDOMWindowInner
+  , private nsIDOMWindow
+  // NOTE: This interface is private, as it's only
+  // implemented on chrome windows.
+  , private nsIDOMChromeWindow
+  , public nsIScriptGlobalObject
+  , public nsIScriptObjectPrincipal
+  , public nsSupportsWeakReference
+  , public nsIInterfaceRequestor
+  , public PRCListStr
+  , public nsAPostRefreshObserver
 {
 public:
   typedef mozilla::TimeStamp TimeStamp;

dom/base/nsGlobalWindowOuter.h

@@ -161,17 +161,18 @@ extern const js::Class OuterWindowProxyClass;
 // inner windows belonging to the same outer window, but that's an unimportant
 // side effect of inheriting PRCList).
 
-class nsGlobalWindowOuter : public mozilla::dom::EventTarget,
-                            public nsPIDOMWindowOuter,
-                            private nsIDOMWindow,
-                            // NOTE: This interface is private, as it's only
-                            // implemented on chrome windows.
-                            private nsIDOMChromeWindow,
-                            public nsIScriptGlobalObject,
-                            public nsIScriptObjectPrincipal,
-                            public nsSupportsWeakReference,
-                            public nsIInterfaceRequestor,
-                            public PRCListStr
+class nsGlobalWindowOuter final
+  : public mozilla::dom::EventTarget
+  , public nsPIDOMWindowOuter
+  , private nsIDOMWindow
+    // NOTE: This interface is private, as it's only
+    // implemented on chrome windows.
+  , private nsIDOMChromeWindow
+  , public nsIScriptGlobalObject
+  , public nsIScriptObjectPrincipal
+  , public nsSupportsWeakReference
+  , public nsIInterfaceRequestor
+  , public PRCListStr
 {
 public:
   typedef nsDataHashtable<nsUint64HashKey, nsGlobalWindowOuter*> OuterWindowByIdTable;