Remove stale-while-revalidate from net

net/http/http_response_headers.cc

Index: net/http/http_response_headers.cc
diff --git a/net/http/http_response_headers.cc b/net/http/http_response_headers.cc
index d0b2fc18ced38245b5b8397e33a3fe22f4cee804..af308a8ea14e121ab9978c78edc462a2b0f3e362 100644
--- a/net/http/http_response_headers.cc
+++ b/net/http/http_response_headers.cc
@@ -917,28 +917,19 @@ bool HttpResponseHeaders::IsRedirectResponseCode(int response_code) {
 // Of course, there are other factors that can force a response to always be
 // validated or re-fetched.
 //
-// From RFC 5861 section 3, a stale response may be used while revalidation is
-// performed in the background if
-//
-//   freshness_lifetime + stale_while_revalidate > current_age
-//
-ValidationType HttpResponseHeaders::RequiresValidation(
-    const Time& request_time,
-    const Time& response_time,
-    const Time& current_time) const {
+bool HttpResponseHeaders::RequiresValidation(const Time& request_time,
+                                             const Time& response_time,
+                                             const Time& current_time) const {
   FreshnessLifetimes lifetimes = GetFreshnessLifetimes(response_time);
-  if (lifetimes.freshness.is_zero() && lifetimes.staleness.is_zero())
-    return VALIDATION_SYNCHRONOUS;
+  if (lifetimes.freshness.is_zero())
+    return true;
 
   TimeDelta age = GetCurrentAge(request_time, response_time, current_time);
 
   if (lifetimes.freshness > age)
-    return VALIDATION_NONE;
-
-  if (lifetimes.freshness + lifetimes.staleness > age)
-    return VALIDATION_ASYNCHRONOUS;
+    return false;
 
-  return VALIDATION_SYNCHRONOUS;
+  return true;

[mmenke, 2017/03/23 21:39:35]

optional:  Maybe just replace these last 4 lines with:

return lifetime <= GetCurrentAge(request_time, response_time, current_time);

[scottmg, 2017/03/24 22:46:00]

Done. (I was a bit nervous about messing up on a bool, so I was trying to be a
bit conservative.)

 }
 
 // From RFC 2616 section 13.2.4:
@@ -961,9 +952,6 @@ ValidationType HttpResponseHeaders::RequiresValidation(
 //
 //   freshness_lifetime = (date_value - last_modified_value) * 0.10
 //
-// If the stale-while-revalidate directive is present, then it is used to set
-// the |staleness| time, unless it overridden by another directive.
-//
 HttpResponseHeaders::FreshnessLifetimes
 HttpResponseHeaders::GetFreshnessLifetimes(const Time& response_time) const {
   FreshnessLifetimes lifetimes;
@@ -978,13 +966,8 @@ HttpResponseHeaders::GetFreshnessLifetimes(const Time& response_time) const {
     return lifetimes;
   }
 
-  // Cache-Control directive must_revalidate overrides stale-while-revalidate.
   bool must_revalidate = HasHeaderValue("cache-control", "must-revalidate");

[mmenke, 2017/03/23 21:39:35]

Can get rid of the must_revalidate local, and inline the HasHeaderValue call
below.

[scottmg, 2017/03/24 22:46:00]

Done.

 
-  if (must_revalidate || !GetStaleWhileRevalidateValue(&lifetimes.staleness)) {
-    DCHECK_EQ(TimeDelta(), lifetimes.staleness);
-  }
-
   // NOTE: "Cache-Control: max-age" overrides Expires, so we only check the
   // Expires header after checking for max-age in GetFreshnessLifetimes.  This
   // is important since "Expires: <date in the past>" means not fresh, but
@@ -1051,13 +1034,11 @@ HttpResponseHeaders::GetFreshnessLifetimes(const Time& response_time) const {
   if (response_code_ == 300 || response_code_ == 301 || response_code_ == 308 ||
       response_code_ == 410) {
     lifetimes.freshness = TimeDelta::Max();
-    lifetimes.staleness = TimeDelta();  // It should never be stale.
     return lifetimes;
   }
 
   // Our heuristic freshness estimate for this resource is 0 seconds, in
-  // accordance with common browser behaviour. However, stale-while-revalidate
-  // may still apply.
+  // accordance with common browser behaviour.
   DCHECK_EQ(TimeDelta(), lifetimes.freshness);
   return lifetimes;
 }
@@ -1168,11 +1149,6 @@ bool HttpResponseHeaders::GetExpiresValue(Time* result) const {
   return GetTimeValuedHeader("Expires", result);
 }
 
-bool HttpResponseHeaders::GetStaleWhileRevalidateValue(
-    TimeDelta* result) const {
-  return GetCacheControlDirective("stale-while-revalidate", result);
-}
-
 bool HttpResponseHeaders::GetTimeValuedHeader(const std::string& name,
                                               Time* result) const {
   std::string value;