add a flag to enable/disable download interception on android

chrome/browser/android/intercept_download_resource_throttle.h

Index: chrome/browser/android/intercept_download_resource_throttle.h
diff --git a/chrome/browser/android/intercept_download_resource_throttle.h b/chrome/browser/android/intercept_download_resource_throttle.h
index 019407638d141218c68b920a33c3638319edcece..12123c31be6830543299f97508a011d66e7440f1 100644
--- a/chrome/browser/android/intercept_download_resource_throttle.h
+++ b/chrome/browser/android/intercept_download_resource_throttle.h
@@ -19,6 +19,8 @@ namespace chrome {
 // handled by Chrome or passsed to the Android Download Manager.
 class InterceptDownloadResourceThrottle : public content::ResourceThrottle {
  public:
+  static bool IsDownloadInterceptionEnabled();
+
   InterceptDownloadResourceThrottle(net::URLRequest* request,
                                     int render_process_id,
                                     int render_view_id,