Manage IsolatedContext with reference counts

webkit/fileapi/isolated_context.cc

Index: webkit/fileapi/isolated_context.cc
diff --git a/webkit/fileapi/isolated_context.cc b/webkit/fileapi/isolated_context.cc
index e8b52ae83f0ae9bc77904e2934878aac00714bde..adece4277a539b45a47ca7f15b2f487acb8f66ee 100644
--- a/webkit/fileapi/isolated_context.cc
+++ b/webkit/fileapi/isolated_context.cc
@@ -43,15 +43,24 @@ std::string IsolatedContext::RegisterIsolatedFileSystem(
     toplevels.insert(std::make_pair(basename, fullpath));
   }
   toplevel_map_[filesystem_id] = toplevels;
+
+  // Each file system is created with refcount == 0.
+  ref_counts_[filesystem_id] = 0;
+
   return filesystem_id;
 }
 
-// Revoke any registered drag context for the child_id.
-void IsolatedContext::RevokeIsolatedFileSystem(
-    const std::string& filesystem_id) {
+void IsolatedContext::AddReference(const std::string& filesystem_id) {
   base::AutoLock locker(lock_);
-  toplevel_map_.erase(filesystem_id);
-  writable_ids_.erase(filesystem_id);
+  DCHECK(ref_counts_.find(filesystem_id) != ref_counts_.end());
+  ref_counts_[filesystem_id]++;
+}
+
+void IsolatedContext::RemoveReference(const std::string& filesystem_id) {
+  base::AutoLock locker(lock_);

[tzik, 2012/06/21 14:00:35]

Could you add DCHECK(ref_counts_.find(filesystem_id) != ref_counts_.end());?

[kinuko, 2012/06/22 04:53:30]

Done.  We didn't have similar check in RevokeIsolatedFilesystem so I've updated
unittest code not to call extra RemoveReference.  Can you take one more quick
look?

+  // Refcount could become <0 if it has never gotten referenced.
+  if (--ref_counts_[filesystem_id] <= 0)
+    RevokeWithoutLocking(filesystem_id);
 }
 
 bool IsolatedContext::CrackIsolatedPath(const FilePath& virtual_path,
@@ -147,6 +156,13 @@ IsolatedContext::IsolatedContext() {
 IsolatedContext::~IsolatedContext() {
 }
 
+void IsolatedContext::RevokeWithoutLocking(
+    const std::string& filesystem_id) {
+  toplevel_map_.erase(filesystem_id);
+  writable_ids_.erase(filesystem_id);
+  ref_counts_.erase(filesystem_id);
+}
+
 std::string IsolatedContext::GetNewFileSystemId() const {
   // Returns an arbitrary random string which must be unique in the map.
   uint32 random_data[4];