FileChooser: Send null FileChooserResult on canceling a file chooser dialog

instead of empty FileChooserResult.

Receivers of the message, Blink and Pepper, still assume the null
FileChooserResult and the empty FileChooserResult have same meaning.
However this CL makes it possible to fix crbug.com/2508.

This CL doesn't have user-visible behavior changes.

Bug: 2508
Change-Id: I14b17e68116d475d6fd49f4a965d8a6c49418b32
Reviewed-on: https://chromium-review.googlesource.com/c/1343815Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609863}

content/browser/frame_host/render_frame_host_impl.cc

@@ -611,7 +611,7 @@ class FileChooserImpl : public blink::mojom::FileChooser,
     proxy_ = nullptr;
     if (!render_frame_host_)
       return;
-    std::move(callback_).Run(FileChooserResult::New());
+    std::move(callback_).Run(nullptr);
   }
 
  private:

content/renderer/pepper/pepper_file_chooser_host.cc

@@ -47,20 +47,22 @@ class PepperFileChooserHost::CompletionHandler {
   }
 
   void DidChooseFiles(blink::mojom::FileChooserResultPtr result) {
-    DCHECK(result);
     if (host_.get()) {
-      std::vector<blink::mojom::FileChooserFileInfoPtr> mojo_files =
-          std::move(result->files);
       std::vector<PepperFileChooserHost::ChosenFileInfo> files;
-      for (size_t i = 0; i < mojo_files.size(); i++) {
-        base::FilePath file_path = mojo_files[i]->get_native_file()->file_path;
-        // Drop files of which names can not be converted to Unicode. We
-        // can't expose such files in Flash.
-        if (blink::FilePathToWebString(file_path).IsEmpty())
-          continue;
-        files.push_back(PepperFileChooserHost::ChosenFileInfo(
-            file_path,
-            base::UTF16ToUTF8(mojo_files[i]->get_native_file()->display_name)));
+      if (result) {
+        std::vector<blink::mojom::FileChooserFileInfoPtr> mojo_files =
+            std::move(result->files);
+        for (size_t i = 0; i < mojo_files.size(); i++) {
+          base::FilePath file_path =
+              mojo_files[i]->get_native_file()->file_path;
+          // Drop files of which names can not be converted to Unicode. We
+          // can't expose such files in Flash.
+          if (blink::FilePathToWebString(file_path).IsEmpty())
+            continue;
+          files.push_back(PepperFileChooserHost::ChosenFileInfo(
+              file_path, base::UTF16ToUTF8(
+                             mojo_files[i]->get_native_file()->display_name)));
+        }
       }
       host_->StoreChosenFiles(files);
     }

third_party/blink/renderer/core/html/forms/file_chooser.cc

@@ -103,8 +103,11 @@ void FileChooser::EnumerateChosenDirectory() {
 }
 
 void FileChooser::DidChooseFiles(mojom::blink::FileChooserResultPtr result) {
-  DCHECK(result);
-  FileChooserFileInfoList files = std::move(result->files);
+  // TODO(tkent): If |result| is nullptr, we should not clear the
+  // already-selected files in <input type=file> like other browsers.
+  FileChooserFileInfoList files;
+  if (result)
+    files = std::move(result->files);
   // FIXME: This is inelegant. We should not be looking at params_ here.
   if (params_->selected_files.size() == files.size()) {
     bool was_changed = false;
@@ -129,8 +132,10 @@ void FileChooser::DidChooseFiles(mojom::blink::FileChooserResultPtr result) {
     }
   }
 
-  if (client_)
-    client_->FilesChosen(std::move(files), result->base_directory);
+  if (client_) {
+    client_->FilesChosen(std::move(files),
+                         result ? result->base_directory : base::FilePath());
+  }
   DidCloseChooser();
 }