[DragDrop] Set up URL for image search for dropping into omnibox

Sets up the JNI to pass the image search URL and
the post content type. Additionally, calls
AutocompleteDelegate to handle the image search.
The byte array obtained from the drop data is
invalid, which it is empty in this implementation.

Bug: 1459732
Change-Id: Ifbd509f9435e81b249612d219eacac313765f87d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4781614


Reviewed-by: Gang Wu <gangwu@chromium.org>
Reviewed-by: Shu Yang <shuyng@google.com>
Reviewed-by: Wenyu Fu <wenyufu@chromium.org>
Reviewed-by: Theresa Sullivan <twellington@chromium.org>
Commit-Queue: Joel Tan-Aristy <jtanaristy@google.com>
Cr-Commit-Position: refs/heads/main@{#1184826}