Set tab colors in PWAs since they are used for tooltips

Bug: 1053645
Bug: 1053823
Change-Id: I8a9403a1cd4c8d8387b13c932c0772907ed636ff
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2064164
Commit-Queue: Alan Cutter <alancutter@chromium.org>
Reviewed-by: Alan Cutter <alancutter@chromium.org>
Auto-Submit: Joel Hockey <joelhockey@chromium.org>
Cr-Commit-Position: refs/heads/master@{#742917}

chrome/browser/ui/web_applications/app_browser_controller.cc

@@ -410,21 +410,23 @@ void AppBrowserController::UpdateThemePack() {
   // we use the theme for the frame.
   AutogeneratedThemeColors colors;
   SkColor theme_text_color = color_utils::GetColorWithMaxContrast(*theme_color);
+  SkColor alt_color = color_utils::BlendForMinContrast(
+                          *theme_color, *theme_color, base::nullopt,
+                          kAutogeneratedThemeActiveTabPreferredContrast)
+                          .color;
+  SkColor alt_text_color = color_utils::GetColorWithMaxContrast(alt_color);
   if (has_tab_strip_) {
     colors.active_tab_color = *theme_color;
     colors.active_tab_text_color = theme_text_color;
-    colors.frame_color = color_utils::BlendForMinContrast(
-                             *theme_color, *theme_color, base::nullopt,
-                             kAutogeneratedThemeActiveTabPreferredContrast)
-                             .color;
-    colors.frame_text_color =
-        color_utils::GetColorWithMaxContrast(colors.frame_color);
+    colors.frame_color = alt_color;
+    colors.frame_text_color = alt_text_color;
   } else {
-    // Set frame and frame text only.  No tab colors.
+    // Tab colors are used for tooltips.
+    // TODO(crbug.com/1053823): Add tests for theme properties being set in this branch.
     colors.frame_color = *theme_color;
     colors.frame_text_color = theme_text_color;
-    colors.active_tab_color = gfx::kPlaceholderColor;
-    colors.active_tab_text_color = gfx::kPlaceholderColor;
+    colors.active_tab_color = alt_color;
+    colors.active_tab_text_color = alt_text_color;
   }
   BrowserThemePack::BuildFromColors(colors, theme_pack_.get());
 }