Add browser test to the sharing dialog feature in Files.app.

chrome/browser/drive/fake_drive_service.h

Index: chrome/browser/drive/fake_drive_service.h
diff --git a/chrome/browser/drive/fake_drive_service.h b/chrome/browser/drive/fake_drive_service.h
index 9b1a4e51f270de32a54d138e5a3c152ff0d59fab..3cb942e8d0976b9d46549e1d9f228d59b4c6a6bd 100644
--- a/chrome/browser/drive/fake_drive_service.h
+++ b/chrome/browser/drive/fake_drive_service.h
@@ -46,6 +46,12 @@ class FakeDriveService : public DriveServiceInterface {
     default_max_results_ = default_max_results;
   }
 
+  // Sets the url to the test server to be used as a base for generated share
+  // urls to the share dialog.
+  void set_share_url_base(const GURL& share_url_base) {
+    share_url_base_ = share_url_base;
+  }
+
   // Returns the largest changestamp, which starts from 0 by default. See
   // also comments at LoadAccountMetadataForWapi().
   int64 largest_changestamp() const { return largest_changestamp_; }
@@ -274,6 +280,7 @@ class FakeDriveService : public DriveServiceInterface {
   int about_resource_load_count_;
   bool offline_;
   base::FilePath last_cancelled_file_;
+  GURL share_url_base_;
 
   DISALLOW_COPY_AND_ASSIGN(FakeDriveService);
 };