Added experimental Share API on Android behind flag.

third_party/WebKit/public/platform/modules/webshare/webshare.mojom

Index: third_party/WebKit/public/platform/modules/webshare/webshare.mojom
diff --git a/third_party/WebKit/public/platform/modules/webshare/webshare.mojom b/third_party/WebKit/public/platform/modules/webshare/webshare.mojom
index 5291919be8d5c30ec5f33e42684400a30c702993..b96ec30b05e779597ad41a62a8717fb9ac14b05d 100644
--- a/third_party/WebKit/public/platform/modules/webshare/webshare.mojom
+++ b/third_party/WebKit/public/platform/modules/webshare/webshare.mojom
@@ -2,10 +2,14 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+[JavaPackage="org.chromium.mojom.webshare"]
 module blink.mojom;
 
 interface ShareService {
   // The web contents has requested to send a share text action. Returns null on
   // success, or an error message on failure.
+  // TODO(mgiuca): Return an error enum, instead of a string (so the actual
+  // error messages are generated in a single place, rather than many service
+  // handlers).
   Share(string title, string text) => (string? error);
 };