Fix DCHECK in tts_utterance_impl.cc on null browser_context

Bug: 1152873
Test: Run cast_accessibility_unittests
Change-Id: I01dc08d5418d779de60fb1bdf41141b7121d3eed
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2561579Reviewed-by: Sean Topping <seantopping@chromium.org>
Commit-Queue: Daniel Nicoara <dnicoara@chromium.org>
Cr-Commit-Position: refs/heads/master@{#831154}

chromecast/browser/accessibility/flutter/BUILD.gn

@@ -40,6 +40,7 @@ test("cast_accessibility_unittests") {
     "//base/test:run_all_unittests",
     "//chromecast:cast_shell_lib",
     "//chromecast/browser",
+    "//content/test:test_support",
     "//extensions/browser/api",
     "//skia",
     "//testing/gmock",

chromecast/browser/accessibility/flutter/ax_tree_source_flutter_unittest.cc

@@ -11,6 +11,8 @@
 #include "content/public/browser/tts_controller.h"
 #include "content/public/browser/tts_platform.h"
 #include "content/public/common/content_client.h"
+#include "content/public/test/browser_task_environment.h"
+#include "content/public/test/test_browser_context.h"
 #include "extensions/browser/api/automation_internal/automation_event_router_interface.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -121,10 +123,9 @@ class AXTreeSourceFlutterTest : public testing::Test,
                                 public AXTreeSourceFlutter::Delegate {
  public:
   AXTreeSourceFlutterTest()
-      : tree_(
-            std::make_unique<AXTreeSourceFlutter>(this,
-                                                  nullptr /* browser_context */,
-                                                  &router_)) {
+      : tree_(std::make_unique<AXTreeSourceFlutter>(this,
+                                                    &browser_context_,
+                                                    &router_)) {
     // Enable by default.
     tree_->SetAccessibilityEnabled(true);
   }
@@ -206,6 +207,9 @@ class AXTreeSourceFlutterTest : public testing::Test,
  private:
   void OnAction(const ui::AXActionData& data) override {}
 
+  // Required for the TestBrowserContext.
+  content::BrowserTaskEnvironment task_environment_;
+  content::TestBrowserContext browser_context_;
   MockAutomationEventRouter router_;
   std::unique_ptr<AXTreeSourceFlutter> tree_;
 };
@@ -946,6 +950,9 @@ TEST_F(AXTreeSourceFlutterTest, ScopesRouteNoNames) {
   ASSERT_EQ(0, tree_data.focus_id);
   ASSERT_TRUE(mock_tts_platform.GetLastSpokenUtterance() == "");
   EXPECT_EQ(0, GetDispatchedEventCount(ax::mojom::Event::kFocus));
+
+  // Cleanup since the mock will expire at the end of this test.
+  tts_controller->SetTtsPlatform(content::TtsPlatform::GetInstance());
 }
 
 TEST_F(AXTreeSourceFlutterTest, Announce) {
@@ -976,6 +983,9 @@ TEST_F(AXTreeSourceFlutterTest, Announce) {
 
   // Child 3 should have been spoken
   ASSERT_EQ(mock_tts_platform.GetLastSpokenUtterance(), "Say this please");
+
+  // Cleanup since the mock will expire at the end of this test.
+  tts_controller->SetTtsPlatform(content::TtsPlatform::GetInstance());
 }
 
 }  // namespace accessibility