[Native File System] Make "accept" button be default but not focused in permission prompt.

Bug: 985602, 987260
Change-Id: I8ee8c01fed607b42c3bf15a97333652c9c74b2ec
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1730862
Commit-Queue: Victor Costan <pwnall@chromium.org>
Reviewed-by: Victor Costan <pwnall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#684159}

chrome/browser/ui/views/native_file_system/native_file_system_permission_view.cc

@@ -67,7 +67,7 @@ base::string16 NativeFileSystemPermissionView::GetWindowTitle() const {
 }
 
 int NativeFileSystemPermissionView::GetDefaultDialogButton() const {
-  return ui::DIALOG_BUTTON_NONE;
+  return ui::DIALOG_BUTTON_OK;
 }
 
 base::string16 NativeFileSystemPermissionView::GetDialogButtonLabel(
@@ -103,6 +103,10 @@ ui::ModalType NativeFileSystemPermissionView::GetModalType() const {
   return ui::MODAL_TYPE_CHILD;
 }
 
+views::View* NativeFileSystemPermissionView::GetInitiallyFocusedView() {
+  return GetDialogClientView()->cancel_button();
+}
+
 void ShowNativeFileSystemPermissionDialog(
     const url::Origin& origin,
     const base::FilePath& path,

chrome/browser/ui/views/native_file_system/native_file_system_permission_view.h

@@ -53,6 +53,7 @@ class NativeFileSystemPermissionView : public views::DialogDelegateView {
   bool Cancel() override;
   gfx::Size CalculatePreferredSize() const override;
   ui::ModalType GetModalType() const override;
+  views::View* GetInitiallyFocusedView() override;
 
  private:
   NativeFileSystemPermissionView(