Add share_target field to Manifest.

content/public/common/manifest.h

Index: content/public/common/manifest.h
diff --git a/content/public/common/manifest.h b/content/public/common/manifest.h
index d558d66978673f9ce20c4b0284a57818adda63ff..018f3f9a3a09829984e57b5b3c84c5c0b41c1e76 100644
--- a/content/public/common/manifest.h
+++ b/content/public/common/manifest.h
@@ -58,6 +58,18 @@ struct CONTENT_EXPORT Manifest {
     std::vector<IconPurpose> purpose;
   };
 
+  // Structure representing how a Web Share target handles an incoming share.
+  struct CONTENT_EXPORT ShareTarget {
+    ShareTarget();
+    ~ShareTarget();
+
+    bool is_null() const;
+
+    // The URL template that contains placeholders to be replaced with shared
+    // data. Null if the parsing failed.
+    base::NullableString16 url_template;
+  };
+
   // Structure representing a related application.
   struct CONTENT_EXPORT RelatedApplication {
     RelatedApplication();
@@ -107,6 +119,9 @@ struct CONTENT_EXPORT Manifest {
   // icons inside the JSON array were invalid.
   std::vector<Icon> icons;
 
+  // Null if parsing failed or the field was not present.

[Matt Giuca, 2017/01/23 00:18:06]

Document that this field is non-standard and part of a Chrome experiment
(https://github.com/WICG/web-share-target/blob/master/docs/interface.md).

[mlamouri (slow - plz ping), 2017/01/23 00:22:26]

Could you say that this should not be exposed to web contents at the moment
because it's not part of the spec and add a TODO on you and mgiuca?

[constantina, 2017/01/23 02:51:36]

Done.

[constantina, 2017/01/23 02:51:36]

Done.

+  ShareTarget share_target;

[mlamouri (slow - plz ping), 2017/01/23 00:22:26]

Would it make sense to use base::optional<> here? I think it would be clearer
for the consumer of the API that there is no share_target instead of using
`is_null`.

[constantina, 2017/01/23 02:51:36]

Yes, it would. Done.

+
   // Empty if the parsing failed, the field was not present, empty or all the
   // applications inside the array were invalid. The order of the array
   // indicates the priority of the application to use.