Prevent unsafe narrowing: base/files

Bug: 1292951
Change-Id: Ie7489503b41003ec3f4ec97991b39e4d82009c58
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3691384
Reviewed-by: danakj <danakj@chromium.org>
Owners-Override: danakj <danakj@chromium.org>
Commit-Queue: danakj <danakj@chromium.org>
Auto-Submit: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1011590}

diff --git a/base/files/file_util.cc b/base/files/file_util.cc
index a186a6c..b3d4ffc5 100644
--- a/base/files/file_util.cc
+++ b/base/files/file_util.cc

@@ -101,7 +101,8 @@
   std::vector<char> buffer(kBufferSize);
 
   for (;;) {
-    int bytes_read = infile.ReadAtCurrentPos(buffer.data(), buffer.size());
+    int bytes_read =
+        infile.ReadAtCurrentPos(buffer.data(), static_cast<int>(buffer.size()));
     if (bytes_read < 0) {
       return false;
     }
@@ -112,7 +113,8 @@
     int bytes_written_per_read = 0;
     do {
       int bytes_written_partial = outfile.WriteAtCurrentPos(
-          &buffer[bytes_written_per_read], bytes_read - bytes_written_per_read);
+          &buffer[static_cast<size_t>(bytes_written_per_read)],
+          bytes_read - bytes_written_per_read);
       if (bytes_written_partial < 0) {
         return false;
       }
@@ -228,8 +230,8 @@
   // Many files have incorrect size (proc files etc). Hence, the file is read
   // sequentially as opposed to a one-shot read, using file size as a hint for
   // chunk size if available.
-  constexpr int64_t kDefaultChunkSize = 1 << 16;
-  int64_t chunk_size = kDefaultChunkSize - 1;
+  constexpr size_t kDefaultChunkSize = 1 << 16;
+  size_t chunk_size = kDefaultChunkSize - 1;
   ScopedBlockingCall scoped_blocking_call(FROM_HERE, BlockingType::MAY_BLOCK);
 #if BUILDFLAG(IS_WIN)
   BY_HANDLE_FILE_INFORMATION file_info = {};
@@ -237,25 +239,25 @@
           reinterpret_cast<HANDLE>(_get_osfhandle(_fileno(stream))),
           &file_info)) {
     LARGE_INTEGER size;
-    size.HighPart = file_info.nFileSizeHigh;
+    size.HighPart = static_cast<LONG>(file_info.nFileSizeHigh);
     size.LowPart = file_info.nFileSizeLow;
     if (size.QuadPart > 0)
-      chunk_size = size.QuadPart;
+      chunk_size = static_cast<size_t>(size.QuadPart);
   }
 #else   // BUILDFLAG(IS_WIN)
   // In cases where the reported file size is 0, use a smaller chunk size to
   // minimize memory allocated and cost of string::resize() in case the read
   // size is small (i.e. proc files). If the file is larger than this, the read
   // loop will reset |chunk_size| to kDefaultChunkSize.
-  constexpr int64_t kSmallChunkSize = 4096;
+  constexpr size_t kSmallChunkSize = 4096;
   chunk_size = kSmallChunkSize - 1;
   stat_wrapper_t file_info = {};
   if (!File::Fstat(fileno(stream), &file_info) && file_info.st_size > 0)
-    chunk_size = file_info.st_size;
+    chunk_size = static_cast<size_t>(file_info.st_size);
 #endif  // BUILDFLAG(IS_WIN)
   // We need to attempt to read at EOF for feof flag to be set so here we
   // use |chunk_size| + 1.
-  chunk_size = std::min<uint64_t>(chunk_size, max_size) + 1;
+  chunk_size = std::min(chunk_size, max_size) + 1;
   size_t bytes_read_this_pass;
   size_t bytes_read_so_far = 0;
   bool read_status = true;
@@ -345,7 +347,7 @@
 bool TouchFile(const FilePath& path,
                const Time& last_accessed,
                const Time& last_modified) {
-  int flags = File::FLAG_OPEN | File::FLAG_WRITE_ATTRIBUTES;
+  uint32_t flags = File::FLAG_OPEN | File::FLAG_WRITE_ATTRIBUTES;
 
 #if BUILDFLAG(IS_WIN)
   // On Windows, FILE_FLAG_BACKUP_SEMANTICS is needed to open a directory.