Assume all providers may give zero suggest responses.

chrome/browser/autocomplete/shortcuts_provider.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/autocomplete/shortcuts_provider.h"
 
 #include <algorithm>
 #include <cmath>
 #include <map>
 #include <vector>
@@ skipping 49 matching lines @@
   scoped_refptr<ShortcutsBackend> backend =
       ShortcutsBackendFactory::GetForProfile(profile_);
   if (backend.get()) {
     backend->AddObserver(this);
     if (backend->initialized())
       initialized_ = true;
   }
 }
 
 void ShortcutsProvider::Start(const AutocompleteInput& input,
-                              bool minimal_changes) {
+                              bool minimal_changes,
+                              bool called_due_to_focus) {
   matches_.clear();
 
-  if ((input.type() == metrics::OmniboxInputType::INVALID) ||
-      (input.type() == metrics::OmniboxInputType::FORCED_QUERY))
-    return;
-
-  if (input.text().empty())
-    return;
-
-  if (!initialized_)
+  if (called_due_to_focus ||
+      (input.type() == metrics::OmniboxInputType::INVALID) ||
+      (input.type() == metrics::OmniboxInputType::FORCED_QUERY) ||
+      input.text().empty() ||
+      !initialized_)
     return;
 
   base::TimeTicks start_time = base::TimeTicks::Now();
   GetMatches(input);
   if (input.text().length() < 6) {
     base::TimeTicks end_time = base::TimeTicks::Now();
     std::string name = "ShortcutsProvider.QueryIndexTime." +
         base::IntToString(input.text().size());
     base::HistogramBase* counter = base::Histogram::FactoryGet(
         name, 1, 1000, 50, base::Histogram::kUmaTargetedHistogramFlag);
@@ skipping 312 matching lines @@
   // (1.0 / each 5 additional hits), up to a maximum of 5x as long.
   const double kMaxDecaySpeedDivisor = 5.0;
   const double kNumUsesPerDecaySpeedDivisorIncrement = 5.0;
   double decay_divisor = std::min(kMaxDecaySpeedDivisor,
       (shortcut.number_of_hits + kNumUsesPerDecaySpeedDivisorIncrement - 1) /
       kNumUsesPerDecaySpeedDivisorIncrement);
 
   return static_cast<int>((base_score / exp(decay_exponent / decay_divisor)) +
       0.5);
 }