Re-protect custom colors with USE_AURA

In crrev.com/659558, we removed a number of ifdef guards that appeared
to be redundant. Apparently they weren't. Replace what used to be
USE_DEFAULT_RENDER_THEME with USE_AURA (which was equivalent).

Bug: 963366
Change-Id: I1ffcd83e780a92529f5449a014fe7dc06f6fc07b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1612853Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: ccameron <ccameron@chromium.org>
Cr-Commit-Position: refs/heads/master@{#660045}

chrome/browser/renderer_preferences_util.cc

@@ -118,8 +118,6 @@ void UpdateFromSystemSettings(blink::mojom::RendererPreferences* prefs,
   prefs->inactive_selection_bg_color = SkColorSetRGB(0xEA, 0xEA, 0xEA);
   prefs->inactive_selection_fg_color = SK_ColorBLACK;
 #endif
-#else
-  prefs->use_custom_colors = false;
 #endif
 
 #if defined(TOOLKIT_VIEWS)

content/renderer/render_view_impl.cc

@@ -1969,6 +1969,7 @@ void RenderViewImpl::OnSetRendererPrefs(
           : base::TimeDelta::FromMilliseconds(
                 blink::mojom::kDefaultCaretBlinkIntervalInMilliseconds));
 
+#if defined(USE_AURA)
   if (renderer_prefs.use_custom_colors) {
     blink::SetFocusRingColor(renderer_prefs.focus_ring_color);
     blink::SetSelectionColors(renderer_prefs.active_selection_bg_color,
@@ -1978,6 +1979,7 @@ void RenderViewImpl::OnSetRendererPrefs(
     if (webview())
       webview()->MainFrameWidget()->ThemeChanged();
   }
+#endif
 
   if (webview() &&
       old_accept_languages != renderer_preferences_.accept_languages) {