Web Share: Refactor Mojo interface to now return an enum error.

chrome/browser/webshare/share_service_impl.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/webshare/share_service_impl.h"
 
 #include <algorithm>
 #include <functional>
 #include <utility>
 
@@ skipping 181 matching lines @@
 }
 
 void ShareServiceImpl::OnPickerClosed(
     std::unique_ptr<base::DictionaryValue> share_targets,
     const std::string& title,
     const std::string& text,
     const GURL& share_url,
     const ShareCallback& callback,
     base::Optional<std::string> result) {
   if (!result.has_value()) {
-    callback.Run(base::Optional<std::string>("Share was cancelled"));
+    callback.Run(blink::mojom::ShareError::CANCELED);
     return;
   }
 
   std::string chosen_target = result.value();
 
   std::string url_template = GetTargetTemplate(chosen_target, *share_targets);
   std::string url_template_filled;
   if (!ReplacePlaceholders(url_template, title, text, share_url,
                            &url_template_filled)) {
-    callback.Run(base::Optional<std::string>(
-        "Error: unable to replace placeholders in url template"));
+    // TODO(mgiuca): This error should not be possible at share time, because
+    // targets with invalid templates should not be chooseable. Fix
+    // https://crbug.com/694380 and replace this with a DCHECK.
+    callback.Run(blink::mojom::ShareError::INTERNAL_ERROR);
     return;
   }
 
   // The template is relative to the manifest URL (minus the filename).
   // Concatenate to make an absolute URL.
   base::StringPiece url_base(
       chosen_target.data(),
       chosen_target.size() - GURL(chosen_target).ExtractFileName().size());
   const GURL target(url_base.as_string() + 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
   //   invalid UTF-8 sequence (which it can't have).
   // - The replaced pieces: these are escaped.
   // If somehow we slip through this DCHECK, it will just open about:blank.
   DCHECK(target.is_valid());
   OpenTargetURL(target);
 
-  callback.Run(base::nullopt);
+  callback.Run(blink::mojom::ShareError::OK);
 }