Truncate the download file name if it exceeds the filesystem limit.

base/sys_info_win.cc

Index: base/sys_info_win.cc
diff --git a/base/sys_info_win.cc b/base/sys_info_win.cc
index 98d2f7c951bb28605406ce0657793dc91ca711c8..4b7f03827d1a0fd012fe40c7deb554fc92641ff3 100644
--- a/base/sys_info_win.cc
+++ b/base/sys_info_win.cc
@@ -4,9 +4,11 @@
 
 #include "base/sys_info.h"
 
+#include <shlwapi.h>
 #include <windows.h>
 
 #include "base/file_path.h"
+#include "base/file_util.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/stringprintf.h"
@@ -65,6 +67,28 @@ int64 SysInfo::AmountOfFreeDiskSpace(const FilePath& path) {
 }
 
 // static
+int SysInfo::GetMaximumPathComponentLength(const FilePath& path) {
+  base::ThreadRestrictions::AssertIOAllowed();
+  FilePath full_path(path);
+  if (!full_path.IsAbsolute() && !file_util::AbsolutePath(&full_path))
+    return -1;
+
+  // GetVolumeInformationW takes a root path ended with a backslash.
+  std::vector<FilePath::CharType> root(full_path.value().begin(),
+                                       full_path.value().end());
+  root.resize(root.size() + 2);  // +2 for trailing \0 and backslash.
+  PathStripToRootW(&root[0]);
+  PathAddBackslashW(&root[0]);
+
+  DWORD max_length = 0;
+  if (!GetVolumeInformationW(&root[0], NULL, 0, NULL, &max_length, NULL, NULL,
+                             0)) {
+    return -1;
+  }
+  return static_cast<int>(max_length);
+}
+
+// static
 std::string SysInfo::OperatingSystemName() {
   return "Windows NT";
 }