- Add the ability to protect VirtualMemory.

runtime/vm/pages.cc

Index: runtime/vm/pages.cc
===================================================================
--- runtime/vm/pages.cc	(revision 9969)
+++ runtime/vm/pages.cc	(working copy)
@@ -87,6 +87,12 @@
 }
 
 
+void HeapPage::WriteProtect(bool read_only) {
+  memory_->Protect(
+      read_only ? VirtualMemory::kReadOnly : VirtualMemory::kReadWrite);
+}
+
+
 PageSpace::PageSpace(Heap* heap, intptr_t max_capacity, bool is_executable)
     : freelist_(),
       heap_(heap),
@@ -340,6 +346,20 @@
 }
 
 
+void PageSpace::WriteProtect(bool read_only) {
+  HeapPage* page = pages_;
+  while (page != NULL) {
+    page->WriteProtect(read_only);
+    page = page->next();
+  }
+  page = large_pages_;
+  while (page != NULL) {
+    page->WriteProtect(read_only);
+    page = page->next();
+  }
+}
+
+
 void PageSpace::MarkSweep(bool invoke_api_callbacks) {
   // MarkSweep is not reentrant. Make sure that is the case.
   ASSERT(!sweeping_);