[NativeFS] Slightly tweak accepted types in the file dialog.

Rather than sorting all extensions, keep the website provided extensions
first and append the mime-type derived extensions to that list. This
should give the website more control over what extension gets appended
to a file name if the user doesn't include an extension themselves.

Additionally pass 1 as file_type_index, to select the first type by
default. Most file dialog implementations did this anyway when passing
0, but it seems better to be explicit about what type to select by
default.

Bug: 1103133
Change-Id: I531f13e72bdaa4de8d7b3270da21a577ebe56e82
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2288429
Commit-Queue: Marijn Kruisselbrink <mek@chromium.org>
Reviewed-by: Victor Costan <pwnall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#786556}

content/browser/native_file_system/file_system_chooser.cc

@@ -47,30 +47,51 @@ void RecordFileSelectionResult(blink::mojom::ChooseFileSystemEntryType type,
       "NativeFileSystemAPI.FileChooserResult." + TypeToString(type), count);
 }
 
+// Converts the accepted mime types and extensions from |option| into a list
+// of just extensions to be passed to the file dialog implementation.
+// The returned list will start with all the explicit website provided
+// extensions in order, followed by (for each mime type) the preferred
+// extension for that mime type (if any) and any other extensions associated
+// with that mime type. Duplicates are filtered out so each extension only
+// occurs once in the returned list.
 bool GetFileTypesFromAcceptsOption(
     const blink::mojom::ChooseFileSystemEntryAcceptsOption& option,
     std::vector<base::FilePath::StringType>* extensions,
     base::string16* description) {
   std::set<base::FilePath::StringType> extension_set;
 
-  for (const std::string& extension : option.extensions) {
+  for (const std::string& extension_string : option.extensions) {
+    base::FilePath::StringType extension;
 #if defined(OS_WIN)
-    extension_set.insert(base::UTF8ToWide(extension));
+    extension = base::UTF8ToWide(extension_string);
 #else
-    extension_set.insert(extension);
+    extension = extension_string;
 #endif
+    if (extension_set.insert(extension).second) {
+      extensions->push_back(std::move(extension));
+    }
   }
 
   for (const std::string& mime_type : option.mime_types) {
+    base::FilePath::StringType preferred_extension;
+    if (net::GetPreferredExtensionForMimeType(mime_type,
+                                              &preferred_extension)) {
+      if (extension_set.insert(preferred_extension).second) {
+        extensions->push_back(std::move(preferred_extension));
+      }
+    }
+
     std::vector<base::FilePath::StringType> inner;
     net::GetExtensionsForMimeType(mime_type, &inner);
     if (inner.empty())
       continue;
-    extension_set.insert(inner.begin(), inner.end());
+    for (auto& extension : inner) {
+      if (extension_set.insert(extension).second) {
+        extensions->push_back(std::move(extension));
+      }
+    }
   }
 
-  extensions->assign(extension_set.begin(), extension_set.end());
-
   if (extensions->empty())
     return false;
 
@@ -149,7 +170,7 @@ void FileSystemChooser::CreateAndShow(
   listener->dialog_->SelectFile(
       dialog_type, /*title=*/base::string16(),
       /*default_path=*/base::FilePath(), &options.file_type_info(),
-      /*file_type_index=*/0,
+      /*file_type_index=*/1,
       /*default_extension=*/base::FilePath::StringType(),
       web_contents ? web_contents->GetTopLevelNativeWindow() : nullptr,
       /*params=*/nullptr);

content/browser/native_file_system/file_system_chooser_browsertest.cc

@@ -496,9 +496,9 @@ IN_PROC_BROWSER_TEST_F(FileSystemChooserBrowserTest, AcceptsOptions) {
   EXPECT_TRUE(dialog_params.file_types->include_all_files);
   ASSERT_EQ(2u, dialog_params.file_types->extensions.size());
   ASSERT_EQ(2u, dialog_params.file_types->extensions[0].size());
-  EXPECT_EQ(FILE_PATH_LITERAL("Js"),
-            dialog_params.file_types->extensions[0][0]);
   EXPECT_EQ(FILE_PATH_LITERAL("txt"),
+            dialog_params.file_types->extensions[0][0]);
+  EXPECT_EQ(FILE_PATH_LITERAL("Js"),
             dialog_params.file_types->extensions[0][1]);
   EXPECT_TRUE(base::Contains(dialog_params.file_types->extensions[1],
                              FILE_PATH_LITERAL("jpg")));

content/browser/native_file_system/file_system_chooser_unittest.cc

@@ -125,11 +125,11 @@ TEST_F(FileSystemChooserTest, AcceptsExtensions) {
   EXPECT_TRUE(dialog_params.file_types->include_all_files);
   ASSERT_EQ(1u, dialog_params.file_types->extensions.size());
 
-  EXPECT_EQ(2u, dialog_params.file_types->extensions[0].size());
-  EXPECT_TRUE(base::Contains(dialog_params.file_types->extensions[0],
-                             FILE_PATH_LITERAL("text")));
-  EXPECT_TRUE(base::Contains(dialog_params.file_types->extensions[0],
-                             FILE_PATH_LITERAL("js")));
+  ASSERT_EQ(2u, dialog_params.file_types->extensions[0].size());
+  EXPECT_EQ(dialog_params.file_types->extensions[0][0],
+            FILE_PATH_LITERAL("text"));
+  EXPECT_EQ(dialog_params.file_types->extensions[0][1],
+            FILE_PATH_LITERAL("js"));
 
   ASSERT_EQ(1u,
             dialog_params.file_types->extension_description_overrides.size());
@@ -151,8 +151,11 @@ TEST_F(FileSystemChooserTest, AcceptsExtensionsAndMimeTypes) {
   EXPECT_FALSE(dialog_params.file_types->include_all_files);
   ASSERT_EQ(1u, dialog_params.file_types->extensions.size());
 
-  EXPECT_TRUE(base::Contains(dialog_params.file_types->extensions[0],
-                             FILE_PATH_LITERAL("text")));
+  ASSERT_GE(dialog_params.file_types->extensions[0].size(), 4u);
+  EXPECT_EQ(dialog_params.file_types->extensions[0][0],
+            FILE_PATH_LITERAL("text"));
+  EXPECT_EQ(dialog_params.file_types->extensions[0][1],
+            FILE_PATH_LITERAL("jpg"));
   EXPECT_TRUE(base::Contains(dialog_params.file_types->extensions[0],
                              FILE_PATH_LITERAL("gif")));
   EXPECT_TRUE(base::Contains(dialog_params.file_types->extensions[0],