Avoid loading TTS library when not used

This CL fix a startup regression due to loading the voices DLLs early
after startup.

On startup, there a call to TtsControllerImpl::VoicesChanged(...).
The call check whether or not the TTS platform is loaded (TtsPlatformLoading(...)).
Unfortunately, this is accessing the singleton and creating it. The creation
triggers the DLL loading.


Bug: 869399
Change-Id: I639cec62ee176c36aee888413a1a91d893d165b4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2505575Reviewed-by: François Doray <fdoray@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: Etienne Bergeron <etienneb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#822723}

content/browser/speech/tts_controller_impl.cc

@@ -307,7 +307,7 @@ bool TtsControllerImpl::IsSpeaking() {
 }
 
 void TtsControllerImpl::VoicesChanged() {
-  if (TtsPlatformLoading())
+  if (!voices_changed_delegates_.might_have_observers() || TtsPlatformLoading())
     return;
 
   // Existence of platform tts indicates explicit requests to tts. Since

content/browser/speech/tts_controller_unittest.cc

@@ -139,6 +139,11 @@ class MockTtsControllerDelegate : public TtsControllerDelegate {
 };
 #endif
 
+class MockVoicesChangedDelegate : public VoicesChangedDelegate {
+ public:
+  void OnVoicesChanged() override {}
+};
+
 class TestTtsControllerImpl : public TtsControllerImpl {
  public:
   TestTtsControllerImpl() = default;
@@ -170,6 +175,12 @@ class TtsControllerTest : public testing::Test {
 #if defined(OS_CHROMEOS)
     controller()->SetTtsControllerDelegateForTesting(&delegate_);
 #endif
+    controller()->AddVoicesChangedDelegate(&voices_changed_);
+  }
+
+  void TearDown() override {
+    if (controller())
+      controller()->RemoveVoicesChangedDelegate(&voices_changed_);
   }
 
   MockTtsPlatformImpl* platform_impl() { return platform_impl_.get(); }
@@ -216,6 +227,7 @@ class TtsControllerTest : public testing::Test {
 #if defined(OS_CHROMEOS)
   MockTtsControllerDelegate delegate_;
 #endif
+  MockVoicesChangedDelegate voices_changed_;
 };
 
 TEST_F(TtsControllerTest, TestTtsControllerShutdown) {