Don't use global variables for capturing stdio.

runtime/bin/file.h

Index: runtime/bin/file.h
diff --git a/runtime/bin/file.h b/runtime/bin/file.h
index 633c006175fa77f3f081815644e2b4b85f2a5b3e..28e85e3d8ed7996e15fbd6ba5b7d538c598a8e94 100644
--- a/runtime/bin/file.h
+++ b/runtime/bin/file.h
@@ -187,6 +187,18 @@ class File {
   static CObject* StatRequest(const CObjectArray& request);
   static CObject* LockRequest(const CObjectArray& request);
 
+  static void set_capture_stdout(bool value) {
+    capture_stdout_ = value;
+    capture_any_ = (capture_stdout_ || capture_stderr_);
+  }
+  static bool capture_stdout() { return capture_stdout_; }
+
+  static void set_capture_stderr(bool value) {
+    capture_stderr_ = value;
+    capture_any_ = (capture_stdout_ || capture_stderr_);
+  }
+  static bool capture_stderr() { return capture_stderr_; }
+
  private:
   explicit File(FileHandle* handle) : handle_(handle) { }
   void Close();
@@ -196,6 +208,10 @@ class File {
   // FileHandle is an OS specific class which stores data about the file.
   FileHandle* handle_;  // OS specific handle for the file.
 
+  static bool capture_stdout_;
+  static bool capture_stderr_;
+  static bool capture_any_;
+
   DISALLOW_COPY_AND_ASSIGN(File);
 };