Manage IsolatedContext with reference counts

webkit/fileapi/isolated_context.h

Index: webkit/fileapi/isolated_context.h
diff --git a/webkit/fileapi/isolated_context.h b/webkit/fileapi/isolated_context.h
index fa6d0a9ef0011d81c969f509eb0e3b6778611f34..15603281a782c63a56d8580c0dcac9eb00d192bf 100644
--- a/webkit/fileapi/isolated_context.h
+++ b/webkit/fileapi/isolated_context.h
@@ -54,8 +54,20 @@ class FILEAPI_EXPORT IsolatedContext {
   std::string RegisterIsolatedFileSystem(const std::set<FilePath>& fileset);
 
   // Revokes filesystem specified by the given filesystem_id.
+  // Note that this revokes the filesystem no matter how many references it has.
+  // It is ok to call this on the filesystem that has been already deleted
+  // (if its reference count had reached 0).
   void RevokeIsolatedFileSystem(const std::string& filesystem_id);
 
+  // Adds a reference to a filesystem specified by the given filesystem_id.
+  void AddReference(const std::string& filesystem_id);
+
+  // Removes a reference to a filesystem specified by the given filesystem_id.
+  // If the reference count reaches 0 the isolated context gets destroyed.
+  // It is ok to call this on the filesystem that has been already deleted
+  // (e.g. by RevokeIsolatedFileSystem).
+  void RemoveReference(const std::string& filesystem_id);
+
   // Cracks the given |virtual_path| (which should look like
   // "/<filesystem_id>/<relative_path>") and populates the |filesystem_id|
   // and |platform_path| if the embedded <filesystem_id> is registerred
@@ -102,6 +114,10 @@ class FILEAPI_EXPORT IsolatedContext {
   IsolatedContext();
   ~IsolatedContext();
 
+  // Removes the given filesystem without locking.
+  // (The caller must hold a lock)
+  void RevokeWithoutLocking(const std::string& filesystem_id);
+
   // Returns a new filesystem_id.  Called with lock.
   std::string GetNewFileSystemId() const;
 
@@ -118,6 +134,10 @@ class FILEAPI_EXPORT IsolatedContext {
   // security policy manager, e.g. ChildProcessSecurityPolicy.
   std::set<std::string> writable_ids_;
 
+  // Reference counts. Note that an isolated filesystem is created with ref==0.
+  // and will get deleted when the ref count reaches <=0.
+  std::map<std::string, int> ref_counts_;
+
   DISALLOW_COPY_AND_ASSIGN(IsolatedContext);
 };