webshare: Use Resolve to get an absolute URL for the url template

Rather than concatenating we use GURL::Resolve() to get an absolute
URL based on the manifest URL and the url_template.

Change-Id: Id74041fcca6f34a898fc8c9794fc0965a1f4ccd8
Reviewed-on: https://chromium-review.googlesource.com/587704
Commit-Queue: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Reviewed-by: Matt Giuca <mgiuca@chromium.org>
Cr-Commit-Position: refs/heads/master@{#490709}

chrome/browser/webshare/share_service_impl.cc

@@ -191,8 +191,6 @@ void ShareServiceImpl::OnPickerClosed(const std::string& title,
     return;
   }
 
-  const GURL& chosen_target = result->manifest_url();
-
   std::string url_template_filled;
   if (!ReplacePlaceholders(result->url_template(), title, text, share_url,
                            &url_template_filled)) {
@@ -204,12 +202,8 @@ void ShareServiceImpl::OnPickerClosed(const std::string& title,
   }
 
   // The template is relative to the manifest URL (minus the filename).
-  // Concatenate to make an absolute URL.
-  const std::string& chosen_target_spec = chosen_target.spec();
-  base::StringPiece url_base(
-      chosen_target_spec.data(),
-      chosen_target_spec.size() - chosen_target.ExtractFileName().size());
-  const GURL target(url_base.as_string() + url_template_filled);
+  // Resolve it based on the manifest URL to make an absolute URL.
+  const GURL target = result->manifest_url().Resolve(url_template_filled);
   // User should not be able to cause an invalid target URL. Possibilities are:
   // - The base URL: can't be invalid since it's derived from the manifest URL.
   // - The template: can only be invalid if it contains a NUL character or