Give user the ability to disable the URL request throttler:

- Support the command line switch --disable-enforced-throttling. With this switch specified, the URL request throttler won't reject outgoing requests during the back-off peroid. Please note that in this case we still keep track of the back-off period, since we need it to determine retry intervals.
- Add a more detailed error page description for net::ERR_TEMPORARILY_THROTTLED.

BUG=66062
TEST=Without --disable-enforced-throttling switch:
  (1) Type in the addresss bar a URL which is expected to return 5XX.
  (2) Keep clicking the "reload" button.
  (3) After a few clicks, Chrome displays an error page explaining why a net::ERR_TEMPORARILY_THROTTLED error occurs.

With --disable-enforced-throttling switch:
  Following step (1) and (2) described above won't result in a net::ERR_TEMPORARILY_THROTTLED error page.

Review URL: http://codereview.chromium.org/5961008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@70022 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 15 insertions, 2 deletions

diff --git a/net/url_request/url_request_http_job.cc b/net/url_request/url_request_http_job.cc
index 6b8190f..ec0134a 100644
--- a/net/url_request/url_request_http_job.cc
+++ b/net/url_request/url_request_http_job.cc
@@ -696,7 +696,9 @@ void URLRequestHttpJob::StartTransaction() {
     rv = request_->context()->http_transaction_factory()->CreateTransaction(
         &transaction_);
     if (rv == OK) {
-      if (!throttling_entry_->IsDuringExponentialBackoff()) {
+      if (!throttling_entry_->IsDuringExponentialBackoff() ||
+          !net::URLRequestThrottlerManager::GetInstance()->
+              enforce_throttling()) {
         rv = transaction_->Start(
             &request_info_, &start_callback_, request_->net_log());
       } else {
diff --git a/net/url_request/url_request_throttler_manager.cc b/net/url_request/url_request_throttler_manager.cc
index 5428d9a..04e05c9 100644
--- a/net/url_request/url_request_throttler_manager.cc
+++ b/net/url_request/url_request_throttler_manager.cc
@@ -32,7 +32,8 @@ scoped_refptr<URLRequestThrottlerEntryInterface>
 }
 
 URLRequestThrottlerManager::URLRequestThrottlerManager()
-    : requests_since_last_gc_(0) {
+    : requests_since_last_gc_(0),
+      enforce_throttling_(true) {
 }
 
 URLRequestThrottlerManager::~URLRequestThrottlerManager() {
diff --git a/net/url_request/url_request_throttler_manager.h b/net/url_request/url_request_throttler_manager.h
index 6c8cd2f..98211d9 100644
--- a/net/url_request/url_request_throttler_manager.h
+++ b/net/url_request/url_request_throttler_manager.h
@@ -49,6 +49,12 @@ class URLRequestThrottlerManager {
   // It is only used by unit tests.
   void EraseEntryForTests(const GURL& url);
 
+  void set_enforce_throttling(bool enforce_throttling) {
+    enforce_throttling_ = enforce_throttling;
+  }
+
+  bool enforce_throttling() const { return enforce_throttling_; }
+
  protected:
   URLRequestThrottlerManager();
   ~URLRequestThrottlerManager();
@@ -93,6 +99,10 @@ class URLRequestThrottlerManager {
 
   mutable scoped_ptr<GURL::Replacements> url_id_replacements_;
 
+  // Whether we would like to reject outgoing HTTP requests during the back-off
+  // period.
+  bool enforce_throttling_;
+
   DISALLOW_COPY_AND_ASSIGN(URLRequestThrottlerManager);
 };