Trigger style recalc when the window's active state change

Source/core/frame/FrameView.cpp

Index: Source/core/frame/FrameView.cpp
diff --git a/Source/core/frame/FrameView.cpp b/Source/core/frame/FrameView.cpp
index fead2c37d5aef382869754e821fde1e16084b94b..3231af4128ba49c0bec7a0c9b2f4ea177455900f 100644
--- a/Source/core/frame/FrameView.cpp
+++ b/Source/core/frame/FrameView.cpp
@@ -341,6 +341,28 @@ void FrameView::recalculateCustomScrollbarStyle()
     }
 }
 
+void FrameView::invalidateAllCustomScrollbarsOnActiveChanged()
+{
+    const ChildrenWidgetSet* viewChildren = children();
+    bool didStyleChange = false;
+    for (const RefPtrWillBeMember<Widget>& child : *viewChildren) {
+        Widget* widget = child.get();
+        if (widget->isFrameView()) {
+            toFrameView(widget)->recalculateCustomScrollbarStyle();
+            if (toFrameView(widget)->hasCustomScrollbars())

[rune, 2014/12/10 08:29:32]

hasCustomScrollbars() is traversing the whole widget sub-tree in the case where
you have no custom scrollbars. In the case where you find a custom scrollbar and
return from hasCustomScrollbars(), you'll enter and traverse the same widgets
again. This if-check only makes this code more expensive.


How about doing this instead? (I haven't tested that it works):

void FrameView::invalidateAllCustomScrollbarsOnActiveChanged()
{
    const ChildrenWidgetSet* viewChildren = children();
    for (const RefPtrWillBeMember<Widget>& child : *viewChildren) {
        Widget* widget = child.get();
        if (widget->isFrameView())
            toFrameView(widget)->invalidateAllCustomScrollbarsOnActiveChanged();
        else if (widget->isScrollbar())
            toScrollbar(widget)->styleChanged();
    }

    recalculateCustomScrollbarStyle();
}

[MuVen, 2014/12/10 08:44:33]

yes this is much simpler, I have verified all the test, its passing. PTAL of
updated patch with these changes.

+                toFrameView(widget)->invalidateAllCustomScrollbarsOnActiveChanged();
+        } else if (widget->isScrollbar() && toScrollbar(widget)->isCustomScrollbar()) {
+            toScrollbar(widget)->styleChanged();
+            didStyleChange = true;
+        }
+    }
+    if (didStyleChange) {
+        updateScrollbarGeometry();
+        updateScrollCorner();
+        positionScrollbarLayers();
+    }
+}
+
 void FrameView::recalculateScrollbarOverlayStyle()
 {
     ScrollbarOverlayStyle oldOverlayStyle = scrollbarOverlayStyle();