[ MimeHandlerView ] Enable tests on ChromeOS

Many MimeHandlerView browser tests were failing on ChromeOS debug bots
most likely due to the old network path (kNetworkService disabled). This
CL enables all those tests on ChromeOS.

Bug: 949565
Change-Id: I3d9ca747fea2f54d71a88484f72e7b6b55df4a13
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1650041Reviewed-by: James MacLean <wjmaclean@chromium.org>
Commit-Queue: Ehsan Karamad <ekaramad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#667341}

extensions/browser/guest_view/mime_handler_view/mime_handler_view_browsertest.cc

@@ -189,11 +189,6 @@ class MimeHandlerViewCrossProcessTest
   void SetUpCommandLine(base::CommandLine* cl) override {
     MimeHandlerViewTest::SetUpCommandLine(cl);
     is_cross_process_mode_ = GetParam();
-    // TODO(ekaramad): All these tests started timing out on ChromeOS (https://
-    // crbug.com/949565).
-#if defined(OS_CHROMEOS)
-    is_cross_process_mode_ = false;
-#endif
     if (is_cross_process_mode_) {
       scoped_feature_list_.InitAndEnableFeature(
           features::kMimeHandlerViewInCrossProcessFrame);