add a flag to enable/disable download interception on android

chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.cc

Index: chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.cc
diff --git a/chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.cc b/chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.cc
index 0f8a31b584d86bd7990de5e7977ffe6e44236d9b..40c2e26ccd64139a296d5c66c367f55a3ad2a98e 100644
--- a/chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.cc
+++ b/chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.cc
@@ -418,9 +418,11 @@ void ChromeResourceDispatcherHostDelegate::DownloadStarting(
         download_request_limiter_, info->GetWebContentsGetterForRequest(),
         request->url(), request->method()));
 #if BUILDFLAG(ANDROID_JAVA_UI)
-    throttles->push_back(
-        new chrome::InterceptDownloadResourceThrottle(
-            request, child_id, route_id, request_id));
+    if (chrome::InterceptDownloadResourceThrottle::

[svaldez, 2016/02/12 15:21:19]

Consider getting rid of the check here, and instead having
InterceptDownloadResourceThrottle check the IsDownloadInterceptionEnabled and do
nothing if so.

This lets us keep our metrics from InterceptDownloadResourceThrottle.

[qinmin, 2016/02/12 17:27:00]

Done. However, there is a very tiny performance hit as we always need to go
through the throttle for each download.

+        IsDownloadInterceptionEnabled()) {
+      throttles->push_back(new chrome::InterceptDownloadResourceThrottle(
+          request, child_id, route_id, request_id));
+    }
 #endif
   }