Truncate the length of downloaded file name on windows

During annotation, an extra 16 characters(zone identifier)
are appended to the file name.
That may cause the file path to exceed the 260 character limit.
This CL fixes that problem by truncating the file name when generating
it.

BUG=809759

Change-Id: Ie0baa318ccf5824e3ed4df8cf23386653b6747d7
Reviewed-on: https://chromium-review.googlesource.com/919445
Commit-Queue: Min Qin <qinmin@chromium.org>
Reviewed-by: Eric Lawrence <elawrence@chromium.org>
Reviewed-by: David Trainor <dtrainor@chromium.org>
Cr-Commit-Position: refs/heads/master@{#537093}

chrome/browser/download/download_path_reservation_tracker.cc

@@ -48,6 +48,12 @@ typedef std::map<ReservationKey, base::FilePath> ReservationMap;
 // possible filename.
 const size_t kIntermediateNameSuffixLength = sizeof(".crdownload") - 1;
 
+#if defined(OS_WIN)
+// On windows, zone identifier is appended to the downloaded file name during
+// annotation. That increases the length of the final target path.
+const size_t kZoneIdentifierLength = sizeof(":Zone.Identifier") - 1;
+#endif  // defined(OS_WIN)
+
 // Map of download path reservations. Each reserved path is associated with a
 // ReservationKey=DownloadItem*. This object is destroyed in |Revoke()| when
 // there are no more reservations.
@@ -129,8 +135,15 @@ bool CreateUniqueFilename(int max_path_component_length, base::FilePath* path) {
     // If the name length limit is available (max_length != -1), and the
     // the current name exceeds the limit, truncate.
     if (max_path_component_length != -1) {
+#if defined(OS_WIN)
+      int limit =
+          max_path_component_length -
+          std::max(kIntermediateNameSuffixLength, kZoneIdentifierLength) -
+          suffix.size();
+#else
       int limit = max_path_component_length - kIntermediateNameSuffixLength -
                   suffix.size();
+#endif  // defined(OS_WIN)
       // If truncation failed, give up uniquification.
       if (limit <= 0 ||
           !filename_generation::TruncateFilename(&path_to_check, limit))
@@ -178,7 +191,12 @@ PathValidationResult ValidatePathAndResolveConflicts(
   // Check the limit of file name length if it could be obtained. When the
   // suggested name exceeds the limit, truncate or prompt the user.
   if (max_path_component_length != -1) {
+#if defined(OS_WIN)
+    int limit = max_path_component_length -
+                std::max(kIntermediateNameSuffixLength, kZoneIdentifierLength);
+#else
     int limit = max_path_component_length - kIntermediateNameSuffixLength;
+#endif  // defined(OS_WIN)
     if (limit <= 0 ||
         !filename_generation::TruncateFilename(target_path, limit))
       return PathValidationResult::NAME_TOO_LONG;

chrome/browser/download/download_path_reservation_tracker_unittest.cc

@@ -589,9 +589,13 @@ TEST_F(DownloadPathReservationTrackerTest, BasicTruncation) {
       base::GetMaximumPathComponentLength(default_download_path());
   ASSERT_NE(-1, real_max_length);
 
+#if defined(OS_WIN)
+  const size_t max_length = real_max_length - strlen(":Zone.Identifier");
+#else
   // TODO(kinaba): the current implementation leaves spaces for appending
   // ".crdownload". So take it into account. Should be removed in the future.
   const size_t max_length = real_max_length - 11;
+#endif  // defined(OS_WIN)
 
   std::unique_ptr<MockDownloadItem> item(CreateDownloadItem(1));
   base::FilePath path(GetLongNamePathInDownloadsDirectory(
@@ -618,7 +622,11 @@ TEST_F(DownloadPathReservationTrackerTest, TruncationConflict) {
   int real_max_length =
       base::GetMaximumPathComponentLength(default_download_path());
   ASSERT_NE(-1, real_max_length);
+#if defined(OS_WIN)
+  const size_t max_length = real_max_length - strlen(":Zone.Identifier");
+#else
   const size_t max_length = real_max_length - 11;
+#endif  // defined(OS_WIN)
 
   std::unique_ptr<MockDownloadItem> item(CreateDownloadItem(1));
   base::FilePath path(GetLongNamePathInDownloadsDirectory(
@@ -653,7 +661,11 @@ TEST_F(DownloadPathReservationTrackerTest, TruncationFail) {
   int real_max_length =
       base::GetMaximumPathComponentLength(default_download_path());
   ASSERT_NE(-1, real_max_length);
+#if defined(OS_WIN)
+  const size_t max_length = real_max_length - strlen(":Zone.Identifier");
+#else
   const size_t max_length = real_max_length - 11;
+#endif  // defined(OS_WIN)
 
   std::unique_ptr<MockDownloadItem> item(CreateDownloadItem(1));
   base::FilePath path(GetPathInDownloadsDirectory(