Parametrize Suggest polling strategy and delay. Also add a parameter

components/omnibox/search_provider.cc

Index: components/omnibox/search_provider.cc
diff --git a/components/omnibox/search_provider.cc b/components/omnibox/search_provider.cc
index a9cd7b7fe3eef8168757e0ea582ee84243161d40..6bfbfc4698349fa25aee2467d3008e0022d00109 100644
--- a/components/omnibox/search_provider.cc
+++ b/components/omnibox/search_provider.cc
@@ -579,6 +579,21 @@ void SearchProvider::DoHistoryQuery(bool minimal_changes) {
   }
 }
 
+base::TimeDelta SearchProvider::GetSuggestQueryDelay() {
+  bool since_the_last_request = true;

[Mark P, 2014/10/21 21:28:22]

I suggest you don't initialize these two variables here.  Leave it up to
GetSuggestPollingStrategy to set their (default) values correctly.

[Bart N., 2014/10/22 01:19:08]

Done.

+  int polling_delay_ms = 100;
+  OmniboxFieldTrial::GetSuggestPollingStrategy(&since_the_last_request,
+                                               &polling_delay_ms);
+
+  base::TimeDelta delay(base::TimeDelta::FromMilliseconds(polling_delay_ms));
+  if (!since_the_last_request)
+    return delay;
+
+  base::TimeDelta time_since_last_suggest_request =
+      base::TimeTicks::Now() - time_suggest_request_sent_;
+  return std::max(base::TimeDelta(), delay - time_since_last_suggest_request);

[Mark P, 2014/10/21 21:28:22]

You shouldn't need this max.  TimeTicks is supposed to be monotonically
increasing.

[Bart N., 2014/10/22 01:19:08]

What if time_since_last_suggest_request is more than delay? Wouldn't it return a
negative delta? We don't want to wait in this case (thus 0).

[Mark P, 2014/10/22 20:33:06]

Well, negative delays shouldn't wait in any case.  But I see your point that it
makes more sense to return 0 for no delay, not a negative delay (whatever that
means).

[Bart N., 2014/10/22 22:04:56]

Acknowledged.

+}
+
 void SearchProvider::StartOrStopSuggestQuery(bool minimal_changes) {
   if (!IsQuerySuitableForSuggest()) {
     StopSuggest();
@@ -586,6 +601,9 @@ void SearchProvider::StartOrStopSuggestQuery(bool minimal_changes) {
     return;
   }
 
+  if (OmniboxFieldTrial::DisableResultsCaching())
+    ClearAllResults();

[Mark P, 2014/10/21 21:28:22]

For your experiment, do you also want to clear cached answers?

[Bart N., 2014/10/22 01:19:08]

I think so. Do you know why it is not cleared already in ClearAllResults?

[Mark P, 2014/10/22 20:33:06]

Well, my understanding of how answers work is that the answers are stored and
annotated with the query they're attached to.  They're only displayed if we
would normally display a query suggestion that matches something in the answers
cache.  I think this means it's okay to not clear cached answers in this
experiment -- it's not like a suggestion/answer would display at a time
incommensurate with what would've been displayed had no answers been there.  But
I asked because I wanted to reason this out with you.  You will get cached
answers with queries that previously had answers.  That seems reasonable.

[Bart N., 2014/10/22 22:04:56]

Acknowledged.

+
   // For the minimal_changes case, if we finished the previous query and still
   // have its results, or are allowed to keep running it, just do that, rather
   // than starting a new query.
@@ -612,16 +630,16 @@ void SearchProvider::StartOrStopSuggestQuery(bool minimal_changes) {
   if (!input_.want_asynchronous_matches())
     return;
 
-  // To avoid flooding the suggest server, don't send a query until at
-  // least 100 ms since the last query.
-  base::TimeTicks next_suggest_time(time_suggest_request_sent_ +
-      base::TimeDelta::FromMilliseconds(kMinimumTimeBetweenSuggestQueriesMs));
-  base::TimeTicks now(base::TimeTicks::Now());
-  if (now >= next_suggest_time) {
+  // Kick off a timer that will start the URL fetch if it completes before
+  // the user types another character.  Requests may be delayed to avoid
+  // flooding the server with requests that are likely to be thrown away later
+  // anyway.
+  const base::TimeDelta delay = GetSuggestQueryDelay();
+  if (delay <= base::TimeDelta()) {
     Run();
     return;
   }
-  timer_.Start(FROM_HERE, next_suggest_time - now, this, &SearchProvider::Run);
+  timer_.Start(FROM_HERE, delay, this, &SearchProvider::Run);
 }
 
 bool SearchProvider::IsQuerySuitableForSuggest() const {