Fixing transparent pixels appearing black when rendered for the context menu.

chrome/browser/ui/android/context_menu_helper.cc

Index: chrome/browser/ui/android/context_menu_helper.cc
diff --git a/chrome/browser/ui/android/context_menu_helper.cc b/chrome/browser/ui/android/context_menu_helper.cc
index efc1d4db992e670d56e8a6b52e27553df7f635c7..bce9cdbe3ba537ff0647d0869d5014f9a5d11cef 100644
--- a/chrome/browser/ui/android/context_menu_helper.cc
+++ b/chrome/browser/ui/android/context_menu_helper.cc
@@ -238,7 +238,7 @@ void ContextMenuHelper::RetrieveImageInternal(
   // until there's either a connection error or a response.
   auto* thumbnail_capturer_proxy = thumbnail_capturer.get();
   thumbnail_capturer_proxy->RequestThumbnailForContextNode(
-      0, gfx::Size(max_dimen_px, max_dimen_px),
+      0, gfx::Size(max_dimen_px, max_dimen_px), chrome::mojom::ImageFormat::PNG,
       base::Bind(retrieve_callback, base::Passed(&thumbnail_capturer),
                  base::android::ScopedJavaGlobalRef<jobject>(env, jcallback)));
 }