Picker takes a vector of pairs, and passes back the user chosen target.

chrome/browser/webshare/share_service_impl.cc

Index: chrome/browser/webshare/share_service_impl.cc
diff --git a/chrome/browser/webshare/share_service_impl.cc b/chrome/browser/webshare/share_service_impl.cc
index 051bb65c364dad989fdb1038e1723e73991d76d0..40eaf625005159d8a4f13dff495f0ba9bf60e171 100644
--- a/chrome/browser/webshare/share_service_impl.cc
+++ b/chrome/browser/webshare/share_service_impl.cc
@@ -115,8 +115,8 @@ bool ShareServiceImpl::ReplacePlaceholders(base::StringPiece url_template,
 
 void ShareServiceImpl::ShowPickerDialog(
     const std::vector<base::string16>& targets,
-    const base::Callback<void(SharePickerResult)>& callback) {
-  // TODO(mgiuca): Get the browser window as |parent_window|.
+    const base::Callback<void(base::Optional<base::string16>)>& callback) {
+// TODO(mgiuca): Get the browser window as |parent_window|.
 #if defined(OS_LINUX) || defined(OS_WIN)
   chrome::ShowWebShareTargetPickerDialog(nullptr /* parent_window */, targets,
                                          callback);
@@ -139,8 +139,8 @@ void ShareServiceImpl::Share(const std::string& title,
                              const GURL& share_url,
                              const ShareCallback& callback) {
   // TODO(constantina): Replace hard-coded name with the registered target list.
-  constexpr char kTargetName[] = "Web Share Target Test App";
-  std::vector<base::string16> targets{base::ASCIIToUTF16(kTargetName)};
+  constexpr char kUrlBase[] = "https://wicg.github.io/web-share-target/demos/";
+  std::vector<base::string16> targets{base::ASCIIToUTF16(kUrlBase)};
 
   ShowPickerDialog(targets, base::Bind(&ShareServiceImpl::OnPickerClosed,
                                        base::Unretained(this), title, text,
@@ -151,16 +151,14 @@ void ShareServiceImpl::OnPickerClosed(const std::string& title,
                                       const std::string& text,
                                       const GURL& share_url,
                                       const ShareCallback& callback,
-                                      SharePickerResult result) {
-  if (result == SharePickerResult::CANCEL) {
+                                      base::Optional<base::string16> result) {
+  if (!result.has_value()) {
     callback.Run(base::Optional<std::string>("Share was cancelled"));

[sky, 2017/01/31 05:22:32]

Shouldn't this run the callback with no value and let the callback decide how to
interpret it?

[Matt Giuca, 2017/01/31 07:28:02]

There are two different callbacks at play here with different semantics: the
incoming one (which is given an Optional<string16>; previously got a
SharePickerResult) gets nullopt if cancelled, or else the URL template. The
outgoing one, |callback|, gets nullopt if successful or else an error message
string. (That outgoing callback is defined by the mojom long ago.)

So it makes sense here to be converting a nullopt (cancellation) into a non-null
string (error message).

     return;
   }
 
-  // TODO(constantina): replace hard-coded URL with one from user-chosen site.
-  constexpr char kUrlBase[] = "https://wicg.github.io/web-share-target/";
   constexpr char kUrlTemplate[] =
-      "demos/sharetarget.html?title={title}&text={text}&url={url}";
+      "sharetarget.html?title={title}&text={text}&url={url}";
 
   std::string url_template_filled;
   if (!ReplacePlaceholders(kUrlTemplate, title, text, share_url,
@@ -170,7 +168,8 @@ void ShareServiceImpl::OnPickerClosed(const std::string& title,
     return;
   }
 
-  GURL target_url(kUrlBase + url_template_filled);
+  std::string url_base = base::UTF16ToASCII(result.value());
+  GURL target_url(url_base + url_template_filled);
   if (!target_url.is_valid()) {
     callback.Run(base::Optional<std::string>(
         "Error: url of share target is not a valid url."));