Adds an IOSWebViewTypeParam() method to SearchTermsData.

This method returns the type of the iOS webview currently in use, formatted as a
cgi param suitable for appending to omnibox queries.

This CL also updates the corresponding experimental flags methods to cache the
current experiment state, since the state will soon be queried often when
constructing omnibox results.

BUG=551851
TEST=None

Review URL: https://codereview.chromium.org/1495643002

Cr-Commit-Position: refs/heads/master@{#362773}
(cherry picked from commit 4b79d93)

Review URL: https://codereview.chromium.org/1492163004 .

Cr-Commit-Position: refs/branch-heads/2564@{#218}
Cr-Branched-From: 1283eca-refs/heads/master@{#359700}

components/search_engines/search_terms_data.cc

@@ -76,6 +76,10 @@ std::string SearchTermsData::NTPIsThemedParam() const {
   return std::string();
 }
 
+std::string SearchTermsData::IOSWebViewTypeParam() const {
+  return std::string();
+}
+
 std::string SearchTermsData::GoogleImageSearchSource() const {
   return std::string();
 }

components/search_engines/search_terms_data.h

@@ -70,6 +70,11 @@ class SearchTermsData {
   // non-empty for UIThreadSearchTermsData.
   virtual std::string NTPIsThemedParam() const;
 
+  // Returns a string indicating which webview is currently in use on iOS,
+  // suitable for adding as a query string param to search requests.  Returns an
+  // empty string if no parameter should be passed along with search requests.
+  virtual std::string IOSWebViewTypeParam() const;
+
   // Returns the value to use for replacements of type
   // GOOGLE_IMAGE_SEARCH_SOURCE.
   virtual std::string GoogleImageSearchSource() const;

ios/chrome/browser/experimental_flags.h

@@ -5,6 +5,8 @@
 #ifndef IOS_CHROME_BROWSER_EXPERIMENTAL_FLAGS_H_
 #define IOS_CHROME_BROWSER_EXPERIMENTAL_FLAGS_H_
 
+#include <string>
+
 // This file can be empty. Its purpose is to contain the relatively short lived
 // declarations required for experimental flags.
 
@@ -30,6 +32,10 @@ bool IsLRUSnapshotCacheEnabled();
 // The returned value will not change within a given session.
 bool IsWKWebViewEnabled();
 
+// Returns a string containing extra params that should be sent along with
+// omnibox search requests.  The returned value contains a leading "&".
+std::string GetWKWebViewSearchParams();
+
 // Whether keyboard commands are supported.
 bool AreKeyboardCommandsEnabled();
 

ios/chrome/browser/experimental_flags.mm

@@ -7,6 +7,7 @@
 
 #include "ios/chrome/browser/experimental_flags.h"
 
+#include <dispatch/dispatch.h>
 #import <Foundation/Foundation.h>
 
 #include <string>
@@ -70,49 +71,84 @@ bool IsLRUSnapshotCacheEnabled() {
                           base::CompareCase::INSENSITIVE_ASCII);
 }
 
-bool IsWKWebViewEnabled() {
-  // If g_wkwebview_trial_eligibility hasn't been set, default it to
-  // ineligibile. This ensures future calls to try to set it will DCHECK.
-  if (g_wkwebview_trial_eligibility == WKWebViewEligibility::UNSET) {
-    g_wkwebview_trial_eligibility = WKWebViewEligibility::INELIGIBLE;
-  }
+// Helper method that returns true if it is safe to check the finch group for
+// the IOSUseWKWebView experiment.  Some users are ineligible to be in the
+// trial, so for those users, this method returns false.  If this method returns
+// false, do not check for the current finch group, as doing so will incorrectly
+// mark the current user as being in the experiment.
+bool CanCheckWKWebViewExperiment() {
+  // True if this user is eligible for the WKWebView experiment and it is ok to
+  // check the experiment group.
+  static bool ok_to_check_finch = false;
+  static dispatch_once_t once;
+  dispatch_once(&once, ^{
+    // If g_wkwebview_trial_eligibility hasn't been set, default it to
+    // ineligible. This ensures future calls to try to set it will DCHECK.
+    if (g_wkwebview_trial_eligibility == WKWebViewEligibility::UNSET) {
+      g_wkwebview_trial_eligibility = WKWebViewEligibility::INELIGIBLE;
+    }
+
+    // If WKWebView isn't supported, don't activate the experiment at all. This
+    // avoids someone being slotted into the WKWebView bucket (and thus
+    // reporting as WKWebView), but actually running UIWebView.
+    if (!web::IsWKWebViewSupported()) {
+      ok_to_check_finch = false;
+      return;
+    }
+
+    // Check for a flag forcing a specific group.  Even ineligible users can be
+    // opted into WKWebView if an override flag is set.
+    base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
+    bool trial_overridden =
+        command_line->HasSwitch(switches::kEnableIOSWKWebView) ||
+        command_line->HasSwitch(switches::kDisableIOSWKWebView);
+
+    // If the user isn't eligible for the trial (i.e., their state is such that
+    // they should not be automatically selected for the group), and there's no
+    // explicit override, don't check the group (again, to avoid having them
+    // report as part of a group at all).
+    if (g_wkwebview_trial_eligibility == WKWebViewEligibility::INELIGIBLE &&
+        !trial_overridden) {
+      ok_to_check_finch = false;
+      return;
+    }
+
+    ok_to_check_finch = true;
+  });
+
+  return ok_to_check_finch;
+}
 
-  // If WKWebView isn't supported, don't activate the experiment at all. This
-  // avoids someone being slotted into the WKWebView bucket (and thus reporting
-  // as WKWebView), but actually running UIWebView.
-  if (!web::IsWKWebViewSupported())
+bool IsWKWebViewEnabled() {
+  if (!CanCheckWKWebViewExperiment()) {
     return false;
+  }
 
-  // Check for a flag forcing a specific group.
+  // Check if the experimental flag is turned on.
   base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
-  bool force_enable = command_line->HasSwitch(switches::kEnableIOSWKWebView);
-  bool force_disable = command_line->HasSwitch(switches::kDisableIOSWKWebView);
-  bool trial_overridden = force_enable || force_disable;
-
-  // If the user isn't eligible for the trial (i.e., their state is such that
-  // they should not be automatically selected for the group), and there's no
-  // explicit override, don't check the group (again, to avoid having them
-  // report as part of a group at all).
-  if (g_wkwebview_trial_eligibility == WKWebViewEligibility::INELIGIBLE &&
-      !trial_overridden)
+  if (command_line->HasSwitch(switches::kEnableIOSWKWebView))
+    return true;
+  else if (command_line->HasSwitch(switches::kDisableIOSWKWebView))
     return false;
 
   // Now that it's been established that user is a candidate, set up the trial
   // by checking the group.
   std::string group_name =
       base::FieldTrialList::FindFullName("IOSUseWKWebView");
 
-  // Check if the experimental flag is turned on.
-  if (force_enable)
-    return true;
-  else if (force_disable)
-    return false;
-
   // Check if the finch experiment is turned on.
   return base::StartsWith(group_name, "Enabled",
                           base::CompareCase::INSENSITIVE_ASCII);
 }
 
+std::string GetWKWebViewSearchParams() {
+  if (!CanCheckWKWebViewExperiment()) {
+    return std::string();
+  }
+
+  return variations::GetVariationParamValue("IOSUseWKWebView", "esrch");
+}
+
 bool AreKeyboardCommandsEnabled() {
   return !base::CommandLine::ForCurrentProcess()->HasSwitch(
       switches::kDisableKeyboardCommands);

ios/chrome/browser/search_engines/ui_thread_search_terms_data.cc

@@ -12,10 +12,12 @@
 #include "components/search/search.h"
 #include "components/version_info/version_info.h"
 #include "ios/chrome/browser/application_context.h"
+#include "ios/chrome/browser/experimental_flags.h"
 #include "ios/chrome/browser/google/google_brand.h"
 #include "ios/chrome/browser/google/google_url_tracker_factory.h"
 #include "ios/chrome/common/channel_info.h"
 #include "ios/web/public/web_thread.h"
+#include "net/base/escape.h"
 #include "url/gurl.h"
 
 #if defined(ENABLE_RLZ)
@@ -119,6 +121,16 @@ std::string UIThreadSearchTermsData::NTPIsThemedParam() const {
   return std::string();
 }
 
+std::string UIThreadSearchTermsData::IOSWebViewTypeParam() const {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  std::string param = experimental_flags::GetWKWebViewSearchParams();
+  if (param.empty()) {
+    return std::string();
+  }
+
+  return "&esrch=" + net::EscapeQueryParamValue(param, true);
+}
+
 std::string UIThreadSearchTermsData::GoogleImageSearchSource() const {
   DCHECK(thread_checker_.CalledOnValidThread());
   std::string version(version_info::GetProductName() + " " +

ios/chrome/browser/search_engines/ui_thread_search_terms_data.h

@@ -31,6 +31,7 @@ class UIThreadSearchTermsData : public SearchTermsData {
   std::string ForceInstantResultsParam(bool for_prerender) const override;
   int OmniboxStartMargin() const override;
   std::string NTPIsThemedParam() const override;
+  std::string IOSWebViewTypeParam() const override;
   std::string GoogleImageSearchSource() const override;
 
  private: