Add on-by-default tracing to FrameView::invalidateTree which adds more debug info

Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 1024 matching lines @@
 // let the compositor pick which to actually draw.
 // See http://crbug.com/306706
 void FrameView::invalidateTree(RenderObject* root)
 {
     ASSERT(RuntimeEnabledFeatures::repaintAfterLayoutEnabled());
     ASSERT(!root->needsLayout());
     // We should only invalidate paints for the outer most layout. This works as
     // we continue to track paint invalidation rects until this function is called.
     ASSERT(!m_nestedLayoutCount);
 
-    TRACE_EVENT1(TRACE_DISABLED_BY_DEFAULT("blink.invalidation"), "FrameView::invalidateTree",
-        "root", TRACE_STR_COPY(root->debugName().ascii().data()));
+    const char* debugData = "unknown";
+    bool isTracing;
+    TRACE_EVENT_CATEGORY_GROUP_ENABLED(TRACE_DISABLED_BY_DEFAULT("blink.invalidation"), &isTracing);
+    if (isTracing)
+        debugData = root->debugName().ascii().data();

[esprehn, 2014/06/07 02:20:40]

All you're trying to do is save the one virtual call and the malloc for the
string here?

Also I don't think this is correct, the CString that created in ascii() will be
free by the time you get to the trace event below which should result in
crashes. You'd need to store the CString in a local.

+    TRACE_EVENT1("blink", "FrameView::invalidateTree", "root", TRACE_STR_COPY(debugData));
 
     // FIXME: really, we're in the paint invalidation phase here, and the compositing queries are legal.
     // Until those states are fully fledged, I'll just disable the ASSERTS.
     DisableCompositingQueryAsserts compositingQueryAssertsDisabler;
 
     RootLayoutStateScope rootLayoutStateScope(*root);
 
     root->invalidateTreeAfterLayout(*root->containerForRepaint());
 
     // Invalidate the paint of the frameviews scrollbars if needed
@@ skipping 2216 matching lines @@
 void FrameView::willRemoveScrollbar(Scrollbar* scrollbar, ScrollbarOrientation orientation)
 {
     ScrollableArea::willRemoveScrollbar(scrollbar, orientation);
     if (AXObjectCache* cache = axObjectCache()) {
         cache->remove(scrollbar);
         cache->handleScrollbarUpdate(this);
     }
 }
 
 } // namespace WebCore