[Harmony Cast Dialog] Change the sink list height limit to 6.5 items

Also use the correct button height const to reflect a recent change.

Bug: 881923
Change-Id: I2553c3d8d891a25b981edce8f0578e516d7ebe43
Reviewed-on: https://chromium-review.googlesource.com/c/1327557Reviewed-by: Brandon Tolsch <btolsch@chromium.org>
Commit-Queue: Takumi Fujimoto <takumif@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606678}

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

@@ -273,8 +273,8 @@ void CastDialogView::ShowScrollView() {
   }
   scroll_view_ = new views::ScrollView();
   AddChildView(scroll_view_);
-  constexpr int kSinkButtonHeight = 50;
-  scroll_view_->ClipHeightTo(0, kSinkButtonHeight * 10);
+  constexpr int kSinkButtonHeight = 56;
+  scroll_view_->ClipHeightTo(0, kSinkButtonHeight * 6.5);
 }
 
 void CastDialogView::RestoreSinkListState() {