[ios] Adds support for parsing Text-to-Speech search results.

ios/chrome/browser/voice/voice_search_url_rewriter.mm

+// Copyright 2016 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.
+
+#import "ios/chrome/browser/voice/voice_search_url_rewriter.h"
+
+#import <Foundation/Foundation.h>
+
+#import "base/mac/scoped_nsobject.h"
+#import "base/strings/sys_string_conversions.h"
+#include "components/google/core/browser/google_util.h"
+#include "components/prefs/pref_service.h"
+#include "ios/chrome/browser/browser_state/chrome_browser_state.h"
+#include "ios/chrome/browser/pref_names.h"
+#include "ios/chrome/browser/voice/speech_input_locale_config.h"
+#include "net/base/url_util.h"
+#include "url/gurl.h"
+
+bool VoiceSearchURLRewriter(GURL* url, web::BrowserState* browser_state) {
+  if (!google_util::IsGoogleSearchUrl(*url))
+    return false;
+
+  ios::ChromeBrowserState* chrome_browser_state =
+      ios::ChromeBrowserState::FromBrowserState(browser_state);
+  std::string language =
+      chrome_browser_state->GetPrefs()->GetString(prefs::kVoiceSearchLocale);
+  GURL rewritten_url(*url);
+  // The |hl| parameter will be overriden only if the voice search locale
+  // is not empty. If it is empty (indicating that voice search locale
+  // uses device language), the |hl| will keep the original value.
+  // If there is no |hl| in the query the |spknlang| will use the application
+  // locale as a fallback (instead of using the same locale for both |hl|
+  // and |spknlang|).
+  if (language.empty()) {
+    voice::SpeechInputLocaleConfig* locale_config =
+        voice::SpeechInputLocaleConfig::GetInstance();
+    if (locale_config)
+      language = locale_config->GetDefaultLocale().code;
+    if (!language.length()) {
+      NOTREACHED();
+      language = "en-US";
+    }
+  }
+  rewritten_url =
+      net::AppendOrReplaceQueryParameter(rewritten_url, "hl", language);
+  rewritten_url =
+      net::AppendQueryParameter(rewritten_url, "spknlang", language);
+  rewritten_url = net::AppendQueryParameter(rewritten_url, "inm", "vs");
+  rewritten_url = net::AppendQueryParameter(rewritten_url, "vse", "1");
+  *url = rewritten_url;
+
+  // Return false so other URLRewriters can update the url if necessary.
+  return false;
+}