[ios] Adds a provider API for AudioSessionController.

ios/chrome/browser/voice/BUILD.gn

Index: ios/chrome/browser/voice/BUILD.gn
diff --git a/ios/chrome/browser/voice/BUILD.gn b/ios/chrome/browser/voice/BUILD.gn
index 5342d5a1382f43bfbf6212ac6e3cad16362bd4e0..cb53b2596fabcb104769906ecc82e303f2136322 100644
--- a/ios/chrome/browser/voice/BUILD.gn
+++ b/ios/chrome/browser/voice/BUILD.gn
@@ -4,6 +4,7 @@
 
 source_set("voice") {
   sources = [
+    "audio_session_controller.h",
     "speech_input_locale.h",
     "speech_input_locale_config.h",
     "speech_input_locale_config.mm",
@@ -19,3 +20,15 @@ source_set("voice") {
     "//ios/public/provider/chrome/browser",
   ]
 }
+
+source_set("test_support") {
+  sources = [
+    "test_audio_session_controller.cc",
+    "test_audio_session_controller.h",
+  ]
+
+  deps = [
+    ":voice",
+    "//base",
+  ]
+}