[Harmony Cast Dialog] Disable the Cast button when all sinks disappear

Clicking on the Cast button when there are no sinks causes a crash.
This CL disables the button when the dialog goes from having sinks to
empty.

Bug: 857224
Change-Id: I8040aef278d28fbc6e6b03c04e9ff9103156ea44
Reviewed-on: https://chromium-review.googlesource.com/1119531Reviewed-by: mark a. foltz <mfoltz@chromium.org>
Commit-Queue: Takumi Fujimoto <takumif@chromium.org>
Cr-Commit-Position: refs/heads/master@{#572304}

chrome/browser/ui/views/media_router/cast_dialog_view.cc

@@ -159,6 +159,8 @@ void CastDialogView::OnModelUpdated(const CastDialogModel& model) {
   }
   dialog_title_ = model.dialog_header();
   MaybeSizeToContents();
+  // Update the main action button.
+  DialogModelChanged();
 }
 
 void CastDialogView::OnControllerInvalidated() {

chrome/browser/ui/views/media_router/cast_dialog_view_unittest.cc

@@ -26,6 +26,7 @@
 #include "ui/events/base_event_utils.h"
 #include "ui/views/controls/scroll_view.h"
 #include "ui/views/widget/widget.h"
+#include "ui/views/window/dialog_client_view.h"
 
 using testing::_;
 using testing::Invoke;
@@ -289,4 +290,19 @@ TEST_F(CastDialogViewTest, ShowNoDeviceView) {
   EXPECT_TRUE(scroll_view()->visible());
 }
 
+TEST_F(CastDialogViewTest, SwitchToNoDeviceView) {
+  // Start with one sink. The main button should be enabled.
+  CastDialogModel model = CreateModelWithSinks({CreateAvailableSink()});
+  InitializeDialogWithModel(model);
+  EXPECT_TRUE(dialog_->GetDialogClientView()->ok_button()->enabled());
+
+  // Remove the sink. The no-device view should be shown, and the main button
+  // should be disabled.
+  model.set_media_sinks({});
+  dialog_->OnModelUpdated(model);
+  EXPECT_TRUE(no_sinks_view()->visible());
+  EXPECT_FALSE(scroll_view());
+  EXPECT_FALSE(dialog_->GetDialogClientView()->ok_button()->enabled());
+}
+
 }  // namespace media_router