Crop images from custom themes before storing them into the theme pack

chrome/browser/themes/theme_service_mac.mm

Index: chrome/browser/themes/theme_service_mac.mm
diff --git a/chrome/browser/themes/theme_service_mac.mm b/chrome/browser/themes/theme_service_mac.mm
index abb441bbea9f68c7c281b8ad7dc370c2669fce85..146558e87214d8646ab5843a003622b96107ade4 100644
--- a/chrome/browser/themes/theme_service_mac.mm
+++ b/chrome/browser/themes/theme_service_mac.mm
@@ -52,9 +52,9 @@ NSImage* ThemeService::GetNSImageNamed(int id, bool allow_default) const {
   // - To get the generated tinted images.
   NSImage* nsimage = nil;
   if (theme_pack_.get()) {
-    const gfx::Image* image = theme_pack_->GetImageNamed(id);
-    if (image)
-      nsimage = image->ToNSImage();
+    gfx::Image image = theme_pack_->GetImageNamed(id);
+    if (!image.IsEmpty())
+      nsimage = image.ToNSImage();
   }
 
   // If the theme didn't override this image then load it from the resource