[Sharesheet] Run file manager browser tests with sharesheet enable.

This CL updates the option.enable_sharesheet default value to be true to
run all tests with sharesheet enabled. This is because we turn on the
sharesheet flags by default.

BUG=1097623

Change-Id: I8714da4bffa30992ca0caf40a34b5237423c34b3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2461666Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Commit-Queue: Maggie Cai <mxcai@chromium.org>
Cr-Commit-Position: refs/heads/master@{#816074}

chrome/browser/chromeos/file_manager/file_manager_browsertest_base.h

@@ -94,7 +94,7 @@ class FileManagerBrowserTestBase : public content::DevToolsAgentHostObserver,
     bool observe_file_tasks = true;
 
     // Whether test should enable sharesheet.
-    bool enable_sharesheet = false;
+    bool enable_sharesheet = true;
 
     // Whether test needs the single partition format feature.
     bool single_partition_format = false;