[BlobAsync] Disk support for blob storage

storage/browser/blob/blob_data_handle.h

Index: storage/browser/blob/blob_data_handle.h
diff --git a/storage/browser/blob/blob_data_handle.h b/storage/browser/blob/blob_data_handle.h
index 3f4529346b103cc0149d0a507494011e867153dc..a174a1b355b6d9543563598d2fb70ce32ca75246 100644
--- a/storage/browser/blob/blob_data_handle.h
+++ b/storage/browser/blob/blob_data_handle.h
@@ -5,6 +5,7 @@
 #ifndef STORAGE_BROWSER_BLOB_BLOB_DATA_HANDLE_H_
 #define STORAGE_BROWSER_BLOB_BLOB_DATA_HANDLE_H_
 
+#include <limits>
 #include <memory>
 #include <string>
 
@@ -39,6 +40,8 @@ class FileSystemContext;
 class STORAGE_EXPORT BlobDataHandle
     : public base::SupportsUserData::Data {
  public:
+  static constexpr uint64_t kUnknownSize = std::numeric_limits<uint64_t>::max();
+
   // True means the blob was constructed successfully, and false means that
   // there was an error, which is reported in the second argument.
   using BlobConstructedCallback =
@@ -77,6 +80,9 @@ class STORAGE_EXPORT BlobDataHandle
   const std::string& content_type() const;
   // May be accessed on any thread.
   const std::string& content_disposition() const;
+  // May be accessed on any thread. In rare cases where the blob is created
+  // as a file from javascript, this will be kUnknownSize.
+  uint64_t size() const;
 
   // This call and the destruction of the returned snapshot must be called
   // on the IO thread. If the blob is broken, then we return a nullptr here.
@@ -94,6 +100,7 @@ class STORAGE_EXPORT BlobDataHandle
     BlobDataHandleShared(const std::string& uuid,
                          const std::string& content_type,
                          const std::string& content_disposition,
+                         uint64_t size,
                          BlobStorageContext* context);
 
    private:
@@ -106,6 +113,7 @@ class STORAGE_EXPORT BlobDataHandle
     const std::string uuid_;
     const std::string content_type_;
     const std::string content_disposition_;
+    const uint64_t size_;
     base::WeakPtr<BlobStorageContext> context_;
 
     DISALLOW_COPY_AND_ASSIGN(BlobDataHandleShared);
@@ -115,6 +123,7 @@ class STORAGE_EXPORT BlobDataHandle
   BlobDataHandle(const std::string& uuid,
                  const std::string& content_type,
                  const std::string& content_disposition,
+                 uint64_t size,
                  BlobStorageContext* context,
                  base::SequencedTaskRunner* io_task_runner);