Move absolute path conversion back to the FILE thread.

In commit 3576d464 the conversion of
the selected directory to an absolute path was moved from
FileSystemChooseEntryFunction::ConfirmDirectoryAccessOnFileThread to
FilesSelected. As the latter runs on the UI thread this violated I/O
restrictions and results in a DCHECK. This was not caught by tests
because in the test environment I/O appears to be allowed on the main
thread.

This change splits the call to IsUnderNonNativeLocalPath from the
conversion to an absolute path.

BUG=457841

Review URL: https://codereview.chromium.org/1023793002

Cr-Commit-Position: refs/heads/master@{#321510}

chrome/browser/extensions/api/file_system/file_system_api.cc

@@ -639,13 +639,10 @@ void FileSystemChooseEntryFunction::FilesSelected(
     content::WebContents* web_contents = app_window->web_contents();
 
     DCHECK_EQ(paths.size(), 1u);
+    bool non_native_path = false;
 #if defined(OS_CHROMEOS)
-    base::FilePath check_path =
-        file_manager::util::IsUnderNonNativeLocalPath(GetProfile(), paths[0])
-            ? paths[0]
-            : base::MakeAbsoluteFilePath(paths[0]);
-#else
-    base::FilePath check_path = base::MakeAbsoluteFilePath(paths[0]);
+    non_native_path =
+        file_manager::util::IsUnderNonNativeLocalPath(GetProfile(), paths[0]);
 #endif
 
     content::BrowserThread::PostTask(
@@ -654,7 +651,7 @@ void FileSystemChooseEntryFunction::FilesSelected(
         base::Bind(
             &FileSystemChooseEntryFunction::ConfirmDirectoryAccessOnFileThread,
             this,
-            check_path,
+            non_native_path,
             paths,
             web_contents));
     return;
@@ -669,9 +666,11 @@ void FileSystemChooseEntryFunction::FileSelectionCanceled() {
 }
 
 void FileSystemChooseEntryFunction::ConfirmDirectoryAccessOnFileThread(
-    const base::FilePath& check_path,
+    bool non_native_path,
     const std::vector<base::FilePath>& paths,
     content::WebContents* web_contents) {
+  const base::FilePath check_path =
+      non_native_path ? paths[0] : base::MakeAbsoluteFilePath(paths[0]);
   if (check_path.empty()) {
     content::BrowserThread::PostTask(
         content::BrowserThread::UI,

chrome/browser/extensions/api/file_system/file_system_api.h

@@ -159,13 +159,13 @@ class FileSystemChooseEntryFunction : public FileSystemEntryFunction {
   void FilesSelected(const std::vector<base::FilePath>& path);
   void FileSelectionCanceled();
 
-  // Check if |check_path|, the canonicalized form of the chosen directory
-  // |paths|, is or is an ancestor of a sensitive directory. If so, show a
-  // dialog to confirm that the user wants to open the directory.
-  // Calls OnDirectoryAccessConfirmed if the directory isn't sensitive or the
-  // user chooses to open it. Otherwise, calls FileSelectionCanceled.
+  // Check if the chosen directory is or is an ancestor of a sensitive
+  // directory. If so, show a dialog to confirm that the user wants to open the
+  // directory. Calls OnDirectoryAccessConfirmed if the directory isn't
+  // sensitive or the user chooses to open it. Otherwise, calls
+  // FileSelectionCanceled.
   void ConfirmDirectoryAccessOnFileThread(
-      const base::FilePath& check_path,
+      bool non_native_path,
       const std::vector<base::FilePath>& paths,
       content::WebContents* web_contents);
   void OnDirectoryAccessConfirmed(const std::vector<base::FilePath>& paths);