Specifies transparent background for the label in TileItemView.

We may not use single background when it's in Athena (it's not
used yet though).

BUG=425717
R=xiyuan@chromium.org
TEST=manually

Review URL: https://codereview.chromium.org/655823005

Cr-Commit-Position: refs/heads/master@{#301007}

ui/app_list/views/tile_item_view.cc

@@ -11,6 +11,7 @@
 #include "ui/app_list/app_list_view_delegate.h"
 #include "ui/app_list/search_result.h"
 #include "ui/app_list/views/app_list_main_view.h"
+#include "ui/base/resource/resource_bundle.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/color_analysis.h"
 #include "ui/gfx/color_utils.h"
@@ -24,6 +25,14 @@ namespace {
 const int kTileSize = 90;
 const int kTileHorizontalPadding = 10;
 
+// In Windows, transparent background color will cause ugly text rendering,
+// therefore kContentsBackgroundColor should be used. See crbug.com/406989
+#if defined(OS_CHROMEOS)
+const SkColor kTitleBackgroundColor = SK_ColorTRANSPARENT;
+#else
+const SkColor kTitleBackgroundColor = app_list::kContentsBackgroundColor;
+#endif
+
 }  // namespace
 
 namespace app_list {
@@ -45,7 +54,7 @@ TileItemView::TileItemView()
   title_->SetAutoColorReadabilityEnabled(false);
   title_->SetEnabledColor(kGridTitleColor);
   title_->set_background(views::Background::CreateSolidBackground(
-      app_list::kContentsBackgroundColor));
+      kTitleBackgroundColor));
   title_->SetFontList(rb.GetFontList(kItemTextFontStyle));
   title_->SetHorizontalAlignment(gfx::ALIGN_CENTER);