DO NOT LAND - Code for debugging excess style recalcs

Source/core/dom/Node.cpp

Index: Source/core/dom/Node.cpp
diff --git a/Source/core/dom/Node.cpp b/Source/core/dom/Node.cpp
index 6ee07157989533cb9597f31627e14b435f3bfc4e..edb5db109c18172385a5760721b9121b41aef6e4 100644
--- a/Source/core/dom/Node.cpp
+++ b/Source/core/dom/Node.cpp
@@ -96,6 +96,9 @@
 #include "wtf/text/CString.h"
 #include "wtf/text/StringBuilder.h"
 
+#include "base/debug/stack_trace.h"
+#include "bindings/v8/ScriptCallStackFactory.h"
+
 using namespace std;
 
 namespace WebCore {
@@ -699,8 +702,43 @@ void Node::markAncestorsWithChildNeedsDistributionRecalc()
         document().scheduleStyleRecalc();
 }
 
+size_t subtreeSize(Node* rootNode)
+{
+    size_t subtreeSize = 1;
+    Node* currentNode = rootNode;
+    while ((currentNode = NodeTraversal::next(*currentNode, rootNode)))
+        subtreeSize++;
+    return subtreeSize;
+}
+
+static void printJSStackTrace()
+{
+    RefPtr<ScriptCallStack> stack = createScriptCallStack(10);
+    if (!stack) {
+        // The last function in the JS stack always seems to be an empty string?
+        // to compensate, print an extra \n here.
+        printf("Not JS triggered.\n\n");
+        return;
+    }
+    printf("JS Stack:\n");
+    for (size_t i = 0; i < stack->size(); i++)
+        printf("%s\n", stack->at(i).functionName().ascii().data());
+    printf("\n");
+}
+
 inline void Node::setStyleChange(StyleChangeType changeType)
 {
+    static const size_t kMinLoggedSize = 100;
+    if (changeType >= SubtreeStyleChange) {
+        size_t nodeCount = subtreeSize(this);
+        if (nodeCount >= kMinLoggedSize) {
+            printf("\n\nINVALIDATED style on tree of %zu nodes (threshold: %zu)\n", nodeCount, kMinLoggedSize);
+            printf("Root: %s\n\n", debugName().ascii().data());
+            printJSStackTrace();
+            printf("C++ Stack:\n");
+            base::debug::StackTrace().Print();
+        }
+    }
     m_nodeFlags = (m_nodeFlags & ~StyleChangeMask) | changeType;
 }