net: Move the logic reading upload elements to UploadData::Element.

net/base/upload_data.h

Index: net/base/upload_data.h
diff --git a/net/base/upload_data.h b/net/base/upload_data.h
index d42ffad16352f8e7be97fc08f0b8f8440af87d44..02e07ee46fedebc2927907f6610e9a3b5af789a6 100644
--- a/net/base/upload_data.h
+++ b/net/base/upload_data.h
@@ -110,13 +110,27 @@ class NET_EXPORT UploadData : public base::RefCounted<UploadData> {
     // is returned.  This is done for consistency with Mozilla.
     uint64 GetContentLength();
 
-    // Returns a FileStream opened for reading for this element, positioned at
-    // |file_range_offset_|.  The caller gets ownership and is responsible
-    // for cleaning up the FileStream. Returns NULL if this element is not of
-    // type TYPE_FILE or if the file is not openable.
-    FileStream* NewFileStreamForReading();
+    // Reads up to |buf_len| bytes synchronously. Returns the number of bytes
+    // read. This function never fails. If there's less data to read than we
+    // initially observed, then pad with zero (this can happen with files).
+    int ReadSync(char* buf, int buf_len);
+
+    // Returns the number of bytes remaining to read.
+    uint64 BytesRemaining();
 
    private:
+    // Returns a FileStream opened for reading for this element, positioned
+    // at |file_range_offset_|. Returns NULL if the file is not openable.
+    FileStream* OpenFileStream();
+
+    // Reads up to |buf_len| bytes synchronously from memory (i.e. type_ is
+    // TYPE_BYTES or TYPE_CHUNK).
+    int ReadFromMemorySync(char* buf, int buf_len);
+
+    // Reads up to |buf_len| bytes synchronously from a file (i.e. type_ is
+    // TYPE_FILE).
+    int ReadFromFileSync(char* buf, int buf_len);
+
     // Allows tests to override the result of GetContentLength.
     void SetContentLength(uint64 content_length) {
       override_content_length_ = true;
@@ -134,6 +148,12 @@ class NET_EXPORT UploadData : public base::RefCounted<UploadData> {
     bool override_content_length_;
     bool content_length_computed_;
     uint64 content_length_;
+
+    // The byte offset from the beginning of the element data. Used to track
+    // the current position when reading data.
+    size_t offset_;
+
+    // The stream of the element data, if this element is of TYPE_FILE.
     FileStream* file_stream_;
 
     FRIEND_TEST_ALL_PREFIXES(UploadDataStreamTest, FileSmallerThanLength);