Allow offsets in blobs larger than 2GB on 32 bit Chromium builds.

The recent patch crrev.com/895933007 introduced a regression by using size_t
for offsets, which on 32bit builds is sizeof(size_t) = 4 which was causing
broken offset values due to assigning a uint64_t variable to such variables.

This CL fixes that by simply converting the types to uint64_t.

TEST=*FileSystemProvider*BigFile* on a 32 bit build Chromium build with
    chromeos=1.
BUG=375297, 458122

Review URL: https://codereview.chromium.org/959113002

Cr-Commit-Position: refs/heads/master@{#318808}

2 files changed, 7 insertions, 7 deletions

diff --git a/storage/browser/blob/blob_storage_context.cc b/storage/browser/blob/blob_storage_context.cc
index 5170ceb..b673930 100644
--- a/storage/browser/blob/blob_storage_context.cc
+++ b/storage/browser/blob/blob_storage_context.cc
@@ -375,8 +375,8 @@ bool BlobStorageContext::AppendAllocatedBlobItem(
 bool BlobStorageContext::AppendBlob(
     const std::string& target_blob_uuid,
     const InternalBlobData& blob,
-    size_t offset,
-    size_t length,
+    uint64_t offset,
+    uint64_t length,
     InternalBlobData::Builder* target_blob_builder) {
   DCHECK(length > 0);
 
@@ -395,10 +395,10 @@ bool BlobStorageContext::AppendBlob(
   for (; iter != items.end() && length > 0; ++iter) {
     scoped_refptr<ShareableBlobDataItem> shareable_item = iter->get();
     const BlobDataItem& item = *(shareable_item->item());
-    size_t item_length = item.length();
+    uint64_t item_length = item.length();
     DCHECK_GT(item_length, offset);
-    size_t current_length = item_length - offset;
-    size_t new_length = current_length > length ? length : current_length;
+    uint64_t current_length = item_length - offset;
+    uint64_t new_length = current_length > length ? length : current_length;
 
     bool reusing_blob_item = offset == 0 && new_length == item.length();
     UMA_HISTOGRAM_BOOLEAN("Storage.Blob.ReusedItem", reusing_blob_item);
diff --git a/storage/browser/blob/blob_storage_context.h b/storage/browser/blob/blob_storage_context.h
index 175e9002..cf73c8a 100644
--- a/storage/browser/blob/blob_storage_context.h
+++ b/storage/browser/blob/blob_storage_context.h
@@ -122,8 +122,8 @@ class STORAGE_EXPORT BlobStorageContext
   // have to split an item.
   bool AppendBlob(const std::string& target_blob_uuid,
                   const InternalBlobData& blob,
-                  size_t offset,
-                  size_t length,
+                  uint64_t offset,
+                  uint64_t length,
                   InternalBlobData::Builder* target_blob_data);
 
   bool IsInUse(const std::string& uuid);