[omnibox] Add doc provider parameters for supporting max query limit.

With this CL, the doc provider will have 6 query-length related parameters:

DocumentProviderMin(Max)QueryLength
  Limits for which inputs the provider will make a request to the drive backend.
  This is useful to relieving backend load.

DocumentProviderMin(Max)QueryShowLength
  Limits for which inputs the provider will show doc suggestions (assuming the
  backend returned documents). These help analyze experiments by allowing
  observing the effect of changing |min(max)_query_length_| while keeping data
  populations consistent.

DocumentProviderMin(Max)QueryLogLength
  Limits for which inputs the provider will log
  field_trial_triggered_(in_session_). These help analyze experiments by
  restricting data populations to avoid noise when only interested in a range of
  input lengths. E.g. experimenting with |max_query_show_length_| would affect
  only the small subset of long queries.

Bug: 1015977, 864302
Change-Id: Iacb16d8b67b4adeb20e3e73d8570d45e0174d33a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1869374
Commit-Queue: manuk hovanesian <manukh@chromium.org>
Reviewed-by: Tommy Li <tommycli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#708816}

components/omnibox/browser/document_provider.cc

@@ -340,6 +340,10 @@ base::string16 TitleForAutocompletion(AutocompleteMatch match) {
          base::UTF8ToUTF16(" - " + match.destination_url.spec());
 }
 
+bool WithinBounds(int value, int min, int max) {
+  return value >= min && (value < max || max == -1);
+}
+
 }  // namespace
 
 // static
@@ -454,9 +458,9 @@ void DocumentProvider::Start(const AutocompleteInput& input,
   }
 
   // Experiment: don't issue queries for inputs under some length.
-  if (input.text().length() < min_query_length_) {
+  if (!WithinBounds(input.text().length(), min_query_length_,
+                    max_query_length_))
     return;
-  }
 
   // Don't issue queries for input likely to be a URL.
   if (IsInputLikelyURL(input)) {
@@ -544,11 +548,31 @@ DocumentProvider::DocumentProvider(AutocompleteProviderClient* client,
               omnibox::kDocumentProvider,
               "DocumentProviderMinQueryLength",
               4))),
+      max_query_length_(
+          static_cast<size_t>(base::GetFieldTrialParamByFeatureAsInt(
+              omnibox::kDocumentProvider,
+              "DocumentProviderMaxQueryLength",
+              -1))),
       min_query_show_length_(
           static_cast<size_t>(base::GetFieldTrialParamByFeatureAsInt(
               omnibox::kDocumentProvider,
               "DocumentProviderMinQueryShowLength",
               min_query_length_))),
+      max_query_show_length_(
+          static_cast<size_t>(base::GetFieldTrialParamByFeatureAsInt(
+              omnibox::kDocumentProvider,
+              "DocumentProviderMaxQueryShowLength",
+              max_query_length_))),
+      min_query_log_length_(
+          static_cast<size_t>(base::GetFieldTrialParamByFeatureAsInt(
+              omnibox::kDocumentProvider,
+              "DocumentProviderMinQueryLogLength",
+              min_query_length_))),
+      max_query_log_length_(
+          static_cast<size_t>(base::GetFieldTrialParamByFeatureAsInt(
+              omnibox::kDocumentProvider,
+              "DocumentProviderMaxQueryLogLength",
+              max_query_length_))),
       field_trial_triggered_(false),
       field_trial_triggered_in_session_(false),
       backoff_for_session_(false),
@@ -709,8 +733,21 @@ ACMatches DocumentProvider::ParseDocumentSearchResults(
   // - Inputs of length 5 or more will make drive requests; if drive suggestions
   // are returned, field_trial_triggered will be logged, and, if not in
   // counterfactual, the suggestions will be shown.
-  bool show_doc_suggestions = !in_counterfactual_group &&
-                              input_.text().length() >= min_query_show_length_;
+  bool show_doc_suggestions =
+      !in_counterfactual_group &&
+      WithinBounds(input_.text().length(), min_query_show_length_,
+                   max_query_show_length_);
+  // In order to compare small slices of input length while excluding noise from
+  // the larger group of all input lenghts, |min_query_log_length_| and
+  // |max_query_log_length_| specify the queries that will log
+  // field_trial_triggered. E.g., if |min_query_log_length_| is 50 and
+  // |max_query_log_length_| is -1, only inputs of length 50 or greater which
+  // return a drive suggestions will log field_trial_triggered are returned
+  // while shorter queries will continue to make requests and show suggestions.
+  // This allows an uninterrupted user experience for short queries while
+  // allowing focused analysis of long queries.
+  bool trigger_field_trial = WithinBounds(
+      input_.text().length(), min_query_log_length_, max_query_log_length_);
 
   // Ensure server's suggestions are added with monotonically decreasing scores.
   int previous_score = INT_MAX;
@@ -804,11 +841,12 @@ ACMatches DocumentProvider::ParseDocumentSearchResults(
     const std::string* snippet = result->FindStringPath("snippet.snippet");
     if (snippet)
       match.RecordAdditionalInfo("snippet", *snippet);
-    if (show_doc_suggestions) {
+    if (show_doc_suggestions)
       matches.push_back(match);
+    if (trigger_field_trial) {
+      field_trial_triggered_ = true;
+      field_trial_triggered_in_session_ = true;
     }
-    field_trial_triggered_ = true;
-    field_trial_triggered_in_session_ = true;
   }
   return matches;
 }

components/omnibox/browser/document_provider.h

@@ -158,10 +158,26 @@ class DocumentProvider : public AutocompleteProvider {
       const std::string& modified_timestamp_string,
       base::Time now);
 
-  // Don't request doc suggestions for inputs shorter than |min_query_length_|.
+  // Don't request doc suggestions for inputs shorter than |min_query_length_|
+  // or longer than |max_query_length_|. A value of -1 indicates no limit. These
+  // help limit the load on backend servers.
   const size_t min_query_length_;
-  // Hide doc suggestions for inputs shorter than |min_query_show_length_|.
+  const size_t max_query_length_;
+  // Hide doc suggestions for inputs shorter than |min_query_show_length_| or
+  // longer than |max_query_show_length_|. A value of -1 indicates no limit.
+  // These help analyze experiments by allowing observing the effect of changing
+  // |min(max)_query_length_| while keeping data populations consistent.
   const size_t min_query_show_length_;
+  const size_t max_query_show_length_;
+  // Don't log doc suggestions for inputs shorter than |min_query_log_length_|
+  // or longer than |max_query_log_length_| (i.e. don't trigger
+  // field_trial_triggered and field_trial_triggered_in_session). A value of -1
+  // indicates no limit. These help analyze experiments by restricting data
+  // populations to avoid noise when only interested in a range of input
+  // lengths. E.g. experimenting with |max_query_show_length_| would affect only
+  // the small subset of long queries.
+  const size_t min_query_log_length_;
+  const size_t max_query_log_length_;
 
   // Whether a field trial has triggered for this query and this session,
   // respectively. Works similarly to BaseSearchProvider, though this class does