Make Isolated file system writable only if it is configured so

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 cc9e925585b2dc26c3543bc026f19e448954c0b2..e8b52ae83f0ae9bc77904e2934878aac00714bde 100644
--- a/webkit/fileapi/isolated_context.cc
+++ b/webkit/fileapi/isolated_context.cc
@@ -51,6 +51,7 @@ void IsolatedContext::RevokeIsolatedFileSystem(
     const std::string& filesystem_id) {
   base::AutoLock locker(lock_);
   toplevel_map_.erase(filesystem_id);
+  writable_ids_.erase(filesystem_id);
 }
 
 bool IsolatedContext::CrackIsolatedPath(const FilePath& virtual_path,
@@ -97,7 +98,7 @@ bool IsolatedContext::CrackIsolatedPath(const FilePath& virtual_path,
   return true;
 }
 
-bool IsolatedContext::GetTopLevelPaths(std::string filesystem_id,
+bool IsolatedContext::GetTopLevelPaths(const std::string& filesystem_id,
                                        std::vector<FilePath>* paths) const {
   DCHECK(paths);
   base::AutoLock locker(lock_);
@@ -114,6 +115,23 @@ bool IsolatedContext::GetTopLevelPaths(std::string filesystem_id,
   return true;
 }
 
+bool IsolatedContext::SetWritable(const std::string& filesystem_id,
+                                  bool writable) {
+  base::AutoLock locker(lock_);
+  if (toplevel_map_.find(filesystem_id) == toplevel_map_.end())
+    return false;
+  if (writable)
+    writable_ids_.insert(filesystem_id);
+  else
+    writable_ids_.erase(filesystem_id);
+  return true;
+}
+
+bool IsolatedContext::IsWritable(const std::string& filesystem_id) const {
+  base::AutoLock locker(lock_);
+  return (writable_ids_.find(filesystem_id) != writable_ids_.end());
+}
+
 FilePath IsolatedContext::CreateVirtualPath(
     const std::string& filesystem_id, const FilePath& relative_path) const {
   FilePath full_path;