Exclude files from FileSelectChooser if they can't convert to WebStrings.

content/renderer/render_frame_impl.cc

Index: content/renderer/render_frame_impl.cc
diff --git a/content/renderer/render_frame_impl.cc b/content/renderer/render_frame_impl.cc
index 9cfedcf3d3cd1f8e59ae3c803f5cd51dda910520..2ff5f4b8d799ad9e1d16dbe8f878262df0fce214 100644
--- a/content/renderer/render_frame_impl.cc
+++ b/content/renderer/render_frame_impl.cc
@@ -5755,19 +5755,30 @@ void RenderFrameImpl::OnFileChooserResponse(
   if (file_chooser_completions_.empty())
     return;
 
+  // Exclude files whose paths can't be converted into WebStrings.  Blink won't
+  // be able to handle these, and the browser process would kill the renderer
+  // when it claims to have chosen an empty file path.
+  std::vector<content::FileChooserFileInfo> filtered_files;
+  for (const auto& file : files) {
+    if (!blink::FilePathToWebString(file.file_path).IsEmpty())
+      filtered_files.push_back(file);
+  }
+
   // Convert Chrome's SelectedFileInfo list to WebKit's.
   WebVector<blink::WebFileChooserCompletion::SelectedFileInfo> selected_files(
-      files.size());
-  for (size_t i = 0; i < files.size(); ++i) {
+      filtered_files.size());
+  for (size_t i = 0; i < filtered_files.size(); ++i) {
     blink::WebFileChooserCompletion::SelectedFileInfo selected_file;
-    selected_file.path = blink::FilePathToWebString(files[i].file_path);
-    selected_file.display_name =
-        blink::FilePathToWebString(base::FilePath(files[i].display_name));
-    if (files[i].file_system_url.is_valid()) {
-      selected_file.file_system_url = files[i].file_system_url;
-      selected_file.length = files[i].length;
-      selected_file.modification_time = files[i].modification_time.ToDoubleT();
-      selected_file.is_directory = files[i].is_directory;
+    selected_file.path =
+        blink::FilePathToWebString(filtered_files[i].file_path);

[asanka, 2017/04/20 03:05:11]

Nit: Why not skip test with selected_file.path.IsEmpty() here and skip?

[Charlie Reis, 2017/04/20 19:00:38]

Heh, I did try that at first.  :)  AFAICT, WebVector doesn't have any way to
resize or build up arrays of unknown size.  You have to declare its size in
advance and any gaps left over have default constructed objects.

However, Nick pointed out that we could only do an extra pass in the rare case
that we didn't copy over every extra element.  I've switched to that approach. 
(Thanks!)

+    selected_file.display_name = blink::FilePathToWebString(
+        base::FilePath(filtered_files[i].display_name));
+    if (filtered_files[i].file_system_url.is_valid()) {
+      selected_file.file_system_url = filtered_files[i].file_system_url;
+      selected_file.length = filtered_files[i].length;
+      selected_file.modification_time =
+          filtered_files[i].modification_time.ToDoubleT();
+      selected_file.is_directory = filtered_files[i].is_directory;
     }
     selected_files[i] = selected_file;
   }