Limit the number of history urls indexed for omnibox suggestions.

components/omnibox/browser/omnibox_field_trial.cc

Index: components/omnibox/browser/omnibox_field_trial.cc
diff --git a/components/omnibox/browser/omnibox_field_trial.cc b/components/omnibox/browser/omnibox_field_trial.cc
index 378027ff0bc2748b7e25fac1086ed2b30034d053..b575b5165010a97f6cb1ab8fcfe83a7189db8294 100644
--- a/components/omnibox/browser/omnibox_field_trial.cc
+++ b/components/omnibox/browser/omnibox_field_trial.cc
@@ -631,6 +631,17 @@ int OmniboxFieldTrial::GetPhysicalWebAfterTypingBaseRelevance() {
   return 700;
 }
 
+// static
+int OmniboxFieldTrial::MaxNumHQPUrlsIndexedAtStartup() {

[Mark P, 2017/05/10 17:23:09]

nit: .cc function order should match .h order

(I do appreciate you not moving this function originally so I could see the diff
during the review.)

[ssid, 2017/05/10 19:47:58]

Sorry. I actually forgot to move this.

+  std::string param_value(variations::GetVariationParamValue(
+      kBundledExperimentFieldTrialName, kMaxNumHQPUrlsIndexedAtStartupParam));
+  int num_urls;
+  if (!param_value.empty() && base::StringToInt(param_value, &num_urls))

[sdefresne, 2017/05/10 08:59:41]

nit: base::StringToInt returns false for empty strings, so the
"!param_value.empty()" check can be removed

[ssid, 2017/05/10 19:47:58]

Done. Also some other functions have similar checks. Not removing them in this
cl. Eg: GetPhysicalWebAfterTypingBaseRelevance

+    return num_urls;
+  // Default value is set to -1 for unlimited number of urls.
+  return -1;
+}
+
 // static
 bool OmniboxFieldTrial::InZeroSuggestRedirectToChromeFieldTrial() {
   return base::FeatureList::IsEnabled(omnibox::kZeroSuggestRedirectToChrome);
@@ -726,6 +737,9 @@ const char OmniboxFieldTrial::kPhysicalWebZeroSuggestBaseRelevanceParam[] =
 const char OmniboxFieldTrial::kPhysicalWebAfterTypingBaseRelevanceParam[] =
     "PhysicalWebAfterTypingBaseRelevanceParam";
 
+const char OmniboxFieldTrial::kMaxNumHQPUrlsIndexedAtStartupParam[] =
+    "MaxNumHQPUrlsIndexedAtStartup";
+
 const char OmniboxFieldTrial::kZeroSuggestRedirectToChromeServerAddressParam[] =
     "ZeroSuggestRedirectToChromeServerAddress";
 const char