Add experimental support for tracing the state of the VM heap to a file

src/api.cc

Index: src/api.cc
===================================================================
--- src/api.cc	(revision 9457)
+++ src/api.cc	(working copy)
@@ -525,6 +525,70 @@
 }
 
 
+class internal::HeapVisualizerImplementation {
+ public:
+  static void Register(HeapVisualizer* that);
+  static void Deregister(HeapVisualizer* that);
+};
+
+
+void RegisterHeapVisualizer(HeapVisualizer* that) {
+  i::HeapVisualizerImplementation::Register(that);
+}
+
+
+void DeRegisterHeapVisualizer(HeapVisualizer* that) {
+  i::HeapVisualizerImplementation::Deregister(that);
+}
+
+
+void v8::internal::HeapVisualizerImplementation::Register(
+    HeapVisualizer* that) {
+  Heap* heap = Isolate::Current()->heap();
+  heap->UpdateVisualizer(that);
+
+  HeapVisualizer* prev = heap->visualizer();
+  that->set_next(prev);
+  heap->set_visualizer(that);
+}
+
+
+void v8::internal::HeapVisualizerImplementation::Deregister(
+    HeapVisualizer* that) {
+  Heap* heap = Isolate::Current()->heap();
+  HeapVisualizer* prev = NULL;
+  for (HeapVisualizer* current = heap->visualizer();
+       current != NULL;
+       current = current->next()) {
+    if (current == that) {
+      if (prev == NULL) {
+        heap->set_visualizer(that->next());
+      } else {
+        prev->set_next(that->next());
+      }
+      return;
+    }
+  }
+  UNREACHABLE();  // Tried to deregister unregistered visualizer.
+}
+
+
+void v8::HeapVisualizer::WriteX(unsigned char* bytes, int len) {
+  if (kBufferSize - buffer_fullness_ < len) {
+    Flush();
+  }
+  while (len > kBufferSize) {
+    memcpy(buffer_, bytes, kBufferSize);
+    len -= kBufferSize;
+    bytes += kBufferSize;
+    buffer_fullness_ = kBufferSize;
+    Flush();
+  }
+  memcpy(buffer_ + buffer_fullness_, bytes, len);
+  buffer_fullness_ += len;
+}
+
+
 v8::Handle<Primitive> Null() {
   i::Isolate* isolate = i::Isolate::Current();
   if (!EnsureInitializedForIsolate(isolate, "v8::Null()")) {